# Patent

## Title
Method for producing a plant with a high-growth rate

## Abstract

The present invention relates to proteins, OsHDAC1, OsHDAC2 and OsHDAC3, which function as histone deacetylase, a gene coding for said proteins, and a method for producing a plant having a high growth rate by expressing said gene in the plant. According to the present invention, the OsHDACs proteins change the structure of chromatin to increase or decrease the expression of a foreign gene in the genomes, so that the expression amount of the OsHDACs proteins can be controlled to produce a plant having varied phenotypic characteristics. Particularly, the OsHDAC1 protein is expressed locally in the plant and increases the growth rate of plant by its overexpression and its expression is increased by ABA. Therefore, this protein can be very efficiently used for producing plants having a high growth rate even under stress conditions including drought, cold, etc., as well as under normal conditions.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a plant having a high growth rate. More specifically, the present invention relates to proteins, OsHDAC1, OsHDAC2 and OsHDAC3, which function as a histone deacetylase, a gene coding for said proteins, and a method for producing a plant having a high growth rate by expressing said gene in the plant.
2. Description of the Related Art
Acetylation and deacetylation of histone are basic mechanisms to control the transcription of eukaryotic organisms wherein histone acetyltransferases (HATs) loose nucleosome by acetylation of histone to stimulate transcription, and histone deacetylases (HDACs) play a role of inhibiting the transcription through inhibition of the activity of HATs. The HDACs found in mammals can be classified generally into two classes: the HDACs belonging to class I, composed of approximately 400 to 500 amino acids having a homology with RPD3 as histone deacetylase of yeast, and the HDACs belonging to class II, composed of approximately 1000 amino acids having a homology with yeast's HDA1. Up to the present, HDACs have been very extensively studied and are known only in mammals and yeast, whereas plant HDACs have been known only in that they may be related to the failure of phenotypic function in the Arabidopsis and maize plant.
ABA (abscisic acid) is a plant hormone related to various physiological reactions including those against environmental stresses such as seed generation, dormancy or drought, high concentration of salts and cold. It has been known that abscisic acid plays an important role in maintaining the survival of the plant body by inhibiting the germination and growth of seeds and buds when the plant is under unsuitable growth conditions (see, Seo, M. and Koshiba, T., Trends Plant Sci., 7: 41–48, 2002). However, in monocot plants including rice, barley, wheat and maize for food production, it is more important that the productivity be increased by maintaining growth under unsuitable environmental conditions, than the maintenance of survival.
Therefore, there is a continuous need for developing the plant body, which can be maintained at a high growth rate even under stress conditions.
Thus, the present inventors have earnestly and extensively studied to develop a plant body having a high growth rate even under stress conditions. As a result, we have identified that OsHDAC1, among the three kinds of OsHDAC genes isolated from the rice plant, is expressed locally in the whole plant body, and when it is overexpressed, it changes the growth rate and phenotype of the plant and increases the growth of the plant body through increasing its expression even in the presence of ASA which inhibits germination and growth, and thus, completed the present invention.
Ultimately, the main purpose of the present invention is to provide protein OsHDACs that function as a histone deacetylase.
Another purpose of the present invention is to provide a gene OsHDAC coding for said protein.
Further, another purpose of the present invention is to provide a method for producing a plant body having a high growth rate which comprises the step of expressing said OsHDAC genes in the plant body.
SUMMARY OF THE INVENTION
The present invention relates to a protein, OsHDAC1, represented by an amino acid sequence of SEQ. ID. NO. 13 that functions as a histone deacetylase, a gene coding for OsHDAC1 as defined in SEQ. ID. NO. 13, and an OsHDAC1 gene coding for OsHDAC1 as defined in SEQ. ID. NO. 13 and represented by an amino acid sequence of SEQ. ID. NO.1. The present invention also relates to a protein, OsHDAC2, represented by an amino acid sequence of SEQ. ID. NO. 14 that functions as a histone deacetylase, a gene coding for OsHDAC2 as defined in SEQ. ID. NO. 14, and an OsHDAC2 gene coding for OsHDAC2 as defined in SEQ. ID. NO. 14 and represented by an amino acid sequence of SEQ. ID. NO.2. The present invention further relates to a protein, OsHDAC3, represented by an amino acid sequence of SEQ. ID. NO. 15 that functions as a histone deacetylase, a gene coding for OsHDAC3 as defined in SEQ. ID. NO. 15, and an OsHDAC3 gene coding for OsHDAC3 as defined in SEQ. ID. NO. 15 and represented by an amino acid sequence of SEQ. ID. NO. 3.
In addition, the present invention further relates to a method for producing a plant having a high growth rate, which comprises the step of transforming a monocot plant with a recombinant plasmid containing a gene coding for OsHDAC1, a gene coding for OsHDAC2, or a gene coding for OsHDAC3 to express the protein OsHDAC1, OsHDAC2 or OsHDAC3, respectively. Preferably, the high growth rate monocot plant produced by method of the present invention is rice, barley, wheat or maize. The method for producing a plant having a high growth rate according the present invention, can be further characterized in that the expression of OsHDAC1, OsHDAC2 or OsHDAC3 protein is increased by ASA (abscisic acid). The method for producing plant having a high growth rate according to the present invention is also characterized in that the plant exhibits a change in phenotypic properties. In addition the method for producing a plant having a high growth rate according to the present invention comprises the step of transforming a monocot plant with a recombinant plasmid containing a gene as defined in SEQ ID. NO. 1, SEQ. ID. NO. 2 or SEQ. ID. NO. 3, to express a protein OsHDAC1, OsHDAC2 or OsHDAC3, respectively.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject matter of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying figures in which:
FIG. 1 is a drawing which shows the hybridizing position of probes 1, 2, 3, 4 and 5 in OsHDAC1, OsHDAC2 and OsHDAC3 cDNAs;
FIG. 2 is a drawing, which shows the genetic structures of OsHDAC1, OsHDAC2 and OsHDAC3;
FIG. 3 is a genetic map showing plasmid pAi-OsHDAC1;
FIG. 4 is a photograph showing the result of Northern blot analysis, which demonstrates the level of transcription of leaves, roots and callus cells of ABA-treated Ai::OsHDAC1 rice plant;
FIG. 5 is a photograph showing the result of Northern blot analysis, which demonstrates the effect of TSA on the reduction of acetylated H4 in callus cells of Ai::OsHDAC1 rice plant;
FIGS. 6a, 6b, 6c and 6d are photographs showing the growth and morphological change of Ai::OsHDAC1 rice plant, the change in the growth of leaves, the change of collars, and the change of roots, respectively; and
FIGS. 7a and 7b are the graphs showing the growth of buds and deferential roots of Ai::OsHDAC1 rice plant in the absence and presence of ABA, respectively.



DETAILED DESCRIPTION OF THE INVENTION
The present inventors have paid attention to genes or proteins, which control the transcription of genes, particularly HDACs inhibiting the transcription of genes, as the target for changing the growth of plants. Thus, in order to separate plant HDACs genes we have searched the database for expressed sequence tags of rice plant to isolate three kinds of related genes, which are then designated as ‘OsHDAC1’, ‘OsHDAC2’ and ‘OsHDAC3’, respectively. The EST database contains, randomly, the partial base sequences of genes and genomes but does not have any information on the kinds and functions of genes. Therefore, in order to confirm whether the isolated gene actually plays a role or functions as a HDACs, first, a probe was constructed from an isolated gene and then the related genes were separated from a library of rice genes using said probe and amplified. Then, their base sequences and protein sequences were determined to analyze their structures, and thus it could be identified that respective genes contain the structures and sequences conserved in HDACs of mammals. Further, by carrying out Southern blot and Northern blot analysis using rice genomes and RNAs it has been identified that said three kinds of genes belong to the same category, are present with a single copy number in the genome, and are tissue-specifically expressed only except for OsHDAC1. From immunoblot analysis using histone protein purified from callus of rice plant transformed with OsHDAC1 and anti-tetraacetylated histone H4 antibody, it could also be identified that OsHDAC1 protein expressed from said OsHDAC1 gene acts as the normal HDAC. In view of the above findings, it was demonstrated that OsHDAC1, OsHDAC1 and OsHDAC1 genes isolated from EST database are HDACs gene of rice plant. Said three genes have been registered as GenBank accession numbers AF 513382, AF513383 and AF513384, respectively.
Then, the present inventors have also observed the growth and phenotypic morphological change of Ai::OsHDAC1 rice, which is a rice plant transformed with said OsHDAC1. In view of the growth of the rice plant, it was identified that the OsHDAC1 gene introduced into the transformed Ai::OsHDAC1 rice plant is transcribed at a rate higher than the non-transformed rice plant even under normal conditions, and also is transcribed under the conditions treated with ABA as the growth-inhibiting hormone induced by stresses at a level higher than or comparable to those under normal conditions. For the phenotype, the growth of the leaves, collars and roots, the buds of the seeds and the deferential roots in the Ai::OsHDAC1 rice and the non-transformed rice plants were observed. It could be seen that the leaves and the collars of the Ai::OsHDAC1 rice plant are much more healthy and strong and provide a higher growth rate, in comparison to those of non-transformed rice plant. From the above results, it could be identified that the plant body having a high growth rate can be developed using the OsHDAC1 gene.
The method for producing the plant body having a high growth rate according to the present invention comprises the step of transforming the monocot plant with a recombinant plasmid containing the OsHDACs gene to express the OsHDACs proteins: For this purpose, the OsHDACs gene is the OsHDAC1, OsHDAC2 or OsHDAC3 gene, and the expression amount of the OsHDACs protein expressed from said gene can be increased by ASA (abscisic acid) as one of the plant hormones, which inhibits germination and growth, to increase the growth rate of the plant body and further to change the phenotypic characteristics. The monocot plants to be transformed according to the present invention can include rice, barley, wheat and maize, etc. According to the present invention, the OsHDACs proteins change the structure of chromatin to cause an increase or decrease in the expression of the foreign genes in the genomes, so that the plant body of which the phenotypic characteristics are changed can be produced by controlling the expression amount of the OsHDACs proteins. Particularly, since the OsHDAC1 gene is expressed locally in the plant and increases the growth rate of the plant by its overexpression and its expression is increased by ABA, this gene can be very efficiently used for producing plants having a high growth rate even under stress conditions including drought, cold, etc., as well as under normal conditions.
Hereinafter, the present invention will be more specifically illustrated through the following examples. It will be apparent to a person having an ordinary knowledge in the relevant technical field that these examples are intended only to specifically explain the present invention but are not construed to limit the scope of the present invention.
EXAMPLE 1
Isolation of Genes and Construction of Probes
In order to isolate the HDACs gene of a rice plant, the sequences in the GenBank database were searched to isolate a few cDNA fragments of about 300 to 400 bp. Then, clones containing said respective cDNA fragments were screened from clones of the EST database of rice and DNAs contained in clones were sequenced by means of base sequence analyzer (Applied Biosystems, USA) to determine finally three kinds of the whole cDNA gene sequences. The sequenced genes were designated as ‘OsHDAC1 (SEQ. ID. NO. 1)’, ‘OsHDAC2 (SEQ. ID. NO. 2)’ and ‘OsHDAC3 (SEQ. ID. NO. 3)’, respectively. Then, the probes for searching respective genes in the genome library of the rice plant were constructed. Each of said genetic cDNAs was inserted into SalI-NotI site of pBluescript SKII (Stratagene, USA) to obtain the recombinant plasmid. Then, the recombinant plasmid containing OsHDAC1 cDNA was cleaved with NcoI/BamHI, XhoI/NotI and PstI/NotI to obtain DNA fragments of 392 bp (probe 1, SEQ. ID. NO. 4), 1283 bp (probe 2, SEQ. ID. NO. 5), and 415 bp (probe 3, SEQ. ID. NO. 6), as the probes for OsHDAC1. The probes for OsHDAC2 and OsHDAC3 were obtained using the following primers:
(1) Primers for OsHDAC2 probes











Primer P1:





5′-ACGACCCTGACTCTGATATG-3′;
(SEQ. ID. NO. 7)



 



and



 



Primer R1:



5′-CCATGGTGTTGGATAATTCT-3′
(SEQ. ID. NO. 8)






(2) Primers for OsHDAC3 probes











Primer P2:





5′-CAGCAGCTATGCACCAGAAG-3′;
(SEQ. ID. NO. 9)



 



and



 



Primer R2:



5′-GCCTCCACGTCCAGTATTGC-3′
(SEQ. ID. NO. 10)






As the probes for OsHDAC2 and OsHDAC3, the product produced from reverse transcription by means of RT-PCR system (Promega, USA) using plasmids containing said primers and OsHDAC2 or OsHDAC3 was again amplified with PCR to obtain 292 bp (probe 4, SEQ. ID. NO. 11) and 249 bp (probe 5, SEQ. ID. NO. 12) DNA fragments, which were respectively separated with electrophoresis and then labeled with [α-32P] together with said probe 1, probe 2 and probe 3 for OsHDAC1. FIG. 1 is the drawing which shows the hybridizing position of probes 1, 2, 3, 4 and 5 in OsHDAC1, OsHDAC2 and OsHDAC3 cDNAs wherein Nc, B, Xh, P, N, S and E denote NcoI, BamHI, XhoI, PstI, NotI, SalI and EcoRI sites, respectively.
Meanwhile, by means of the BLAST and NDASTAR programs, the protein sequences of the three kinds of said three cDNA genes were determined. As a result of the sequencing of the respective proteins OsHDAC1 (SEQ. ID. NO. 13), OsHDAC2 (SEQ. ID. NO. 14) and OsHDAC3 (SEQ. ID. NO. 15), it could be identified that the proteins are composed respectively of 518, 498 and 510 amino acids and have the molecular weights of 57.5, 55,9 and 56.5 kDa, and preserve 9 domains conserved in mammal HDAC and histidine residue. Thus, it was determined that the separated genes are HDACs gene belonging to class I. According to this, said three cDNA genes OsHDAC1, OsHDAC2 and OsHDAC3 were registered as rice histone deacetylase genes under GenBank accession numbers AF513382, AF513383 and AF513384, respectively.
EXAMPLE 2
Separation of OsHDAC1 Genomic DNA
The three cDNAs separated above were screened from genome library and amplified: Genome database (Beijing Genome Center) of rice plant (Oryza sativa L. ssp. Indica) was screened using OsHDAC1 cDNA separated above to discover a contiguous sequence 31135 consistent with 5′-terminal and 3528-bp of OsHDAC1. To determine the remaining portion of OsHDAC1 genomic DNA, the following primers P3 and R3 were determined from 3-UTR sequence of OsHDAC1 cDNA using PRIMER DESIGNER 4 program:











Primer P3:





5′-GGTGGTGTCTGAATCTCCTA-3′;
(SEQ. ID. NO. 16)



 



and



 



Primer R3:



5′-AGATGGCATCAGTTACTAAG-3′.
(SEQ. ID. NO. 17)






PCR was conducted using said two primers and genomic DNA of rice plant (Oryza saliva cv. Nipponbare) to amplify genomic DNA of 5.9 kb, and then the amplified DNA was inserted into pGEM-T-Easy vector (Promega, USA) and analyzed for its base sequence.
In the same manner, OsHDAC2 and OsHDAC3 cDNAs and said primers P1 and R1 and P2 and R2 were used to obtain the relevant genomic DNA of which the base sequence was analyzed. Then, the sequences of cDNA and genomic DNA were compared with each other to classify exons and introns of OsHDACs gene. FIG. 2 is a drawing, which shows the genetic structures of OsHDAC1, OsHDAC2 and OsHDAC3 wherein the black box represents exons. As can be seen from FIG. 2, it could be identified that OsHDAC1 and OsHDAC3 contain 7 exons and 6 introns and OsHDAC2 contains 6 exons and 5 introns.
EXAMPLE 3
Isolation and Southern Blot Analysis of Genomic DNA
In order to investigate how many copy numbers of respective OsHDACs genes are present in nice genomes, the genomic DNA was extracted from leaves of rice plant (Oryza sativa ca. Nipponbare) grown in greenhouse by means of guanidine-surfactant lysis method using DNAzolES (Molecular Research Center, USA). 5 μg of genomic DNA was cleaved with 5 kinds of restriction enzymes including HindIII, EcoRI, XbaI, BamHI and XhoI, and then subjected to electrophoresis on 1.0% (w/v) agarose gel, transferred to hybond N+ nylon membrane (Amersham Pharmacia, USA) and hybridized respectively with probes 1, 2, 3, 4 and 5. After hybridization, the membrane was washed, allowed to stand on the intensifying plate for a while and then analyzed with phospho-image analyzer (FLA 3000, Fuji, Japan).
As the result of analysis, it could be identified that OsHDAC2 and OsHDAC3 are the members consisting OsHDAC1 group and OsHDAC1, OsHDAC2 and OsHDAC3 are present at a single copy number in rice genome.
EXAMPLE 4
Isolation and Northern Blot Analysis of RNA
In order to investigate the expression patterns of OsHDAC1, OsHDAC2 and OsHDAC3 in various lice tissues, a total RNA was isolated from callus cells, roots and leaves of rice plant using guanidium/LiCl method. 10 μg of total RNA was denatured in 50% formamide, 2.2 M formaldehyde, 20 mM MOPS [3-(N-morpholino)-propanesulfonic acid] and 0.5 mM EDTA at 70° C. for 5 minutes, subjected to electrophoresis on 1% formaldehyde-agarose gel, transferred to hybond N+ nylon membrane, hybridized respectively with probes 1, 2, 3, 4 and 5, and then analyzed with the same method as in said Southern blot analysis. As the result of analysis, it was identified that the transcription product of OsHDAC1 is expressed in all of leaf, root and callus cells whereas the transcription products of OsHDAC2 and OsHDAC3 are not expressed in leaf tissues. Therefore, it could be seen that OsHDAC2 and OsHDAC3 are expressed specifically in roots and calluses.
EXAMPLE 5
Construction of Vector and Production of Transduced Rice Plant
0.4 kb Ai promoter, as ABA-inducible promoter, composed of ABA (abscisic acid)-reaction complex (ABRC3) from 1.8 kb OsHDAC1 cDNA and barley HVA22 gene (see, Shen, Q. and Ho, T. H., Plant Cell, 7: 295–307, 1995), CAMV 35S minimal promoter containing only −46 to +100 portion, and 5′-UTR from adhI gene of Arabidopsis was inserted into ClaI-NcoI and NcoI-NcoI sites of pSK-RTG promoter (see, Jang, I-C. et al., Mol. Breeding, 5: 453–461, 1999). Next, said plasmid was cleaved with ClaI and NotI to obtain 2.2 kb DNA fragment composed of Ai promoter and OsHDAC1 cDNA, which was then inserted into pSBG-M cleaved with ClaI/NotI to construct plasmid pAi-OsHDAC1 (see, FIG. 3). Rice plant was transformed with the resulting plasmid using Agrobacterium-mediated transformation and then grown in greenhouse. All of 25 rice plants were produced, and most of them were identified as having a proliferative property and a resistance against 0.5% Vasta solution. FIG. 3 is a genetic map showing plasmid pAi-OsHDAC1, wherein Ai-P is ABA-inducible promoter; 3′pinII is 3′-portion of potato protease inhibitor II gene; 35S is 35S promoter; bar is bar gene to exhibit a herbicide resistance; 3′ nos is 3′-portion of nopaline synthase gene; and E, P and N denote EcoRI, PstI and NotI sites, respectively.
Southern and Northern blot analysis of the genomes of Ai::OsHDAC1 rice as transduced rice plant was carried out in the same maimer as above, except that OsHDAC1-specific probe 3 and 586 bp MAR probe b (SEQ. ID. NO. 18) prepared from HindIII DNA fragment of pUC-B1-X1 were used (see, Miynarova, L. et al., Plant Cell, 6:417–426, 1994). As the result of Southern blot and Northern blot analysis, it was identified that OsHDAC1 gene is present at 1 to 3 copy numbers in genomic DNA of Ai::OsHDAC1 rice plant and is expressed in all of rice tissues. The subsequent analysis was carried out with selecting the plant having a single copy number of OsHDAC1.
EXAMPLE 6
Effect of ABA Treatment
While leaves of Ai::OsHDAC1 rice plant produced by above Example 5 was incubated in MS medium with or without 20 μM ABA, a total RNA was isolated from leaves at regular intervals to examine the expression level of OsHDAC1 transcription product. As the result, it was identified that the expression of the transcription product reaches at the maximum level one hour after ABA treatment and rapidly decreases after 6 hours. Then, callus cells, leaves and roots of rice plant were incubated in MS medium with or without 20 μM ABA for one hour, and a total RNA was extracted. FIG. 4 is a photograph showing the result of Northern blot analysis, which demonstrates the level of transcription of leaves, roots and callus cells of ABA-treated Ai::OsHDAC1 rice plant, wherein NT is untransformed rice plant, and lanes 2, 4 and 6 represent respective individuals of Ai::OsHDAC1 rice plant incubated in MS medium with (+) or without (−) 20 μM ABA for one hour. As can be seen from FIG. 4, it could be identified that in case of ABA treatment, the expression level of OsHDAC1 transcription product in Ai::OsHDAC1 rice plant is 2 to 5 times in leaves, 2 to 6 times in roots, and 9 to 15 times in callus cells, as high as that in untransformed rice plant. Further, the same result could be confirmed from Western blot analysis of OsHDAC1 protein.
Meanwhile, in callus cells of Ai::OsHDAC1 rice plant two kinds of OsHDAC1 mRNA similar to those present in callus of untransformed normal rice plant were found. However, in normal callus cells short transcription products were expressed predominantly over long transcription products whereas in callus of Ai::OsHDAC1 rice plant long transcription products were predominant.
EXAMPLE 7
Analysis of Histone Acetylation
In order to investigate acetylation of histone, histone was purified from callus (see, Waterborg, J. H. et al., Arch. Biochem. Biophys. 256:167–178, 1987), mixed with the same amount of staining solution (7.4 M urea, 1.4 M NH3 and 10 mM DTT), and then incubated for 5 hours. The culture was subjected to electrophoresis on acid/urea/Triton (AUT; 1 M acetic acid, 0.5% Triton X-100, 45 mM NH3 and 16% acrylamide) comprising the upper layer gel prepared from 1 M acetic acid, 6.3 M urea and 4.4% acrylamide, in a buffer solution containing 0.2 M glycine and 1 M acetic acid. Next, the immunoblot analysis was conducted using anti-tetra-acetylated histone H4 antibody. As the result, it could be identified that the expression of tetra-acetylated histone H4 is greatly reduced in Ai::OsHDAC1 rice plant, and thus, OsHDAC1 protein expressed from introduced OsHDAC1 gene functions as the normal enzyme.
EXAMPLE 8
Effect of Tricostatin A (TSA) Treatment
Rice callus cells, leaves and roots were incubated in MS medium with (+) or without (−) 20 μM ABA for one hour, transferred to MS medium containing 20 μM ABA and 1 μM TSA, incubated for 1 to 6 hours and then subjected to TSA treatment. Next, about 0.1 g of rice tissues was pulverized, homogenized with a buffer solution containing 50 mM Tris-HCl (pH 8.0), 150 mM NaCl, 10% glycerol, 0.5% Triton X-100, 2 mM phenylmethanesulfonyl fluoride, 1 μg/ml aprotinine, 1 μg/ml pepstatin and 1 μg/ml leupeptin, and then incubated at 4° C. for one hour. After incubation, the mixed solution was centrifuged at 4° C. for 5 minutes, and the protein concentration was determined using Bradford solution (BioRad, USA). The protein extract was separated from 12% SDS gel, transferred to polyvinylidene difluoride (PVDF) membrane (Immobilon-P, Millipore), and then reacted with mouse HDAC1 (mHDAC1), histone H4 (H4), acetylated histone (AcH4), the secondary antibody wherein primary antibody to acetylated histone H4 (AcH4) (Upstate Biotechnology, USA) is combined with alkaline phosphatase. FIG. 5 is a photograph showing the result of Northern blot analysis, which demonstrates the effect of TSA on the reduction of acetylated H4 in callus cells of Ai::OsHDAC1 rice plant in which NT is callus cells of untransformed rice plant, AcH4 is acetylated histone H4, H4 is total histone H4, and PC is a core histone separated from chicken red cells Upstate Biotechnology, USA). As can be seen from FIG. 5, it could be identified that the expression level of tetra-acetylated histone H4 is greatly increased in both of Ai::OsHDAC1 rice plant and untransformed rice plant after TSA treatment but total H4 is substantially not changed. Thus, it was confirmed that the expression of tetra-acetylated histone H4 as reduced in Ai::OsHDAC1 rice plant is increased again by TSA treatment. This means that TSA specifically inhibits histone deacetylase to greatly increase the acetylation of histone.
EXAMPLE 9
Analysis of Phenotypic Characteristics
In order to investigate the effect of overexpression of OsHDAC1 on the phenotype and growth of Ai::OsHDAC1 rice plant, Ai::OsHDAC1 rice plant was incubated as the first generation and then, young seedlings or calluses at the second generation were transferred to MS medium with or without 20 μM ABA and incubated for 2 weeks. After incubation, the whole shape of rice plant, and leaves, collars and roots were observed. As the control group, untransformed rice plant was also observed. FIGS. 6a, 6b, 6c and 6d are photographs showing the growth and morphological change of Ai::OsHDAC1 rice plant, the change in the growth of leaves, the change of collars and the change of roots, respectively. In each drawing, NT denotes untransformed rice plant and lanes 2, 3 and 4 in FIGS. 6b, 6c and 6d denote respective individuals of transformed Ai::OsHDAC1 rice plant. As can be seen from FIG. 6a, untransformed plant exhibited the inhibition of growth in the presence of ABA and was killed after 2 to 3 weeks, whereas Ai::OsHDAC1 rice plant exhibits an increase of growth in the presence of ABA. Further, as can be seen from FIGS. 6b, 6c and 6d, leaves, collars and roots of Ai::OsHDAC1 were very healthy and strong in comparison to those of untransformed lice plant.
Further, buds and deferential roots of T2 seeds were also observed. FIGS. 7a and 7b are the graphs comparatively showing the growths of buds and deferential roots of Ai::OsHDAC1 rice plant and untransformed rice plant in the absence and presence of 20 μM ABA, respectively. As can be seen from FIGS. 7a and 7b, when the plant was incubated in MS medium containing 20 μM ABA, the seeds of Ai::OsHDAC1 rice plant exhibited a very rapid rate of bud germination and deferential root growth in comparison to that of the seeds of untransformed rice. The rice plant transformed with the control vector not containing OsHDAC1 gene did not show the characteristics shown in Ai::OsHDAC1 rice plant.
As specifically explained and demonstrated above, the present invention relates to a protein having a function of histone deacetylase, i.e. OsHDAC1, OsHDAC2 and OsHDAC3, a gene coding for said proteins, and a method for producing a plant having a high growth rate by expressing said gene in the plant. According to the present invention, OsHDACs proteins change the structure of chromatin to increase or decrease the expression of a foreign gene in genomes, so that the expression amount of OsHDACs proteins can be controlled to produce the plant having varied phenotypic characteristics. Particularly, OsHDAC1 gene is expressed locally in the plant and increases the growth rate of plant by its overexpression and its expression is increased by ABA. Therefore, it can be very efficiently used for producing plants having a high growth rate even under stress conditions including drought, cold, etc., as well as under the normal conditions.

## Claims

1. An isolated nucleic acid sequence comprising SEQ ID NO: 1 and coding for OsHDAC1 protein.

2. The sequence of claim 1, encoding a protein having a function of histone deacetylase.

3. A method for producing a plant having an increased growth rate, which comprises the step of transforming a monocot plant with a recombinant plasmid containing an isolated nucleic acid sequence comprising SEQ ID NO: 1 to express a protein OsHDAC1.

4. The method for producing a plant having an increased growth rate according to claim 3, characterized in that the monocot plant is rice, barley, wheat or maize.

5. The method for producing a plant having an increased growth rate according to claim 3, characterized in that the expression of OsHDAC1 protein is increased by ABA (abscisic acid).

6. The method for producing a plant having an increased growth rate according to claim 3, characterized in that the plant exhibits a change in phenotypic properties.

7. A method for producing a plant having an increased growth rate, which comprises the step of transforming a monocot plant with a recombinant plasmid containing an isolated nucleic acid sequence comprising SEO ID NO:1 and encoding a protein having a function of histone deacetylase to express a protein OsHDAC1.