TOKYO INSTITUTE OF TECHNOLOGY
2-12-1, Ookayama, Meguro-ku
Tokyo 152-8550 Japan
http://www.titech.ac.jp/english/

Source:Tokyo Institute of Technology
Center for Public Affairs and Communications

For further information :Professor Hiroyuki Ohta
Earth-Life Science Institute / Graduate School of Bioscience andBiotechnology
Tokyo Institute of Technology
Email: ohta.h.ab@m.titech.ac.jp
Tel: +81-3-5734-3414
Fax: +81-3-5734-3416

PRESS RELEASE
Plant fertility - how hormones get aroundTokyo, February 4, 2015: Researchers at Tokyo Institute of Technology haveidentified a transporter protein at the heart of a number of plant processesassociated with fertility and possibly aging.
Very low quantities of hormones instigate a number of the plant processes needed forsurvival, growth and proliferation - all significant factors affecting crop yield. However
getting the right hormones to the right place is crucial. Recent studies have identified anumber of hormone-transporting proteins that import and export hormones across theplasma membrane into and out of cell, helping to understand certain key processes. Now
researchers at Tokyo Institute of Technology, Tohoku University and the RIKEN Center for
Sustainable Resource Science have identified a protein that is core to a number of theprocesses that control fertility in the small mustard-like plant, Arabidopsis.
Hiroyuki Ohta and his team used gene network analysis to highlight genes that respond tojasmonic acid (JA) – a type of hormone associated with fertility, aging and defence
responses for which so far no transporter protein has been identified. They noticed tightco-expression between the gene encoding GTR1/NPF2.10 protein and JA biosynthesis
genes. Further studies showed that treatment with JA increased GTR1 expression inseedlings confirming the link. Hormone and stamen development was affected in plants
with GTR1 associated mutations and their leaves seemed to turn brown and age in thepresence of JA, suggesting GTR1 affects JA sensitivity.
Further studies suggested that GTR1 plays a key role in the transport of another hormone
gibberellin (GA), because GA treatment fully complemented the defect of gtr1 in stamen
development and fertility. While former research had established that JA and GA were both
key to plant fertility and that there may be crosstalk between the two, the function ofinterplay had not been well established. Treating JA-deficient mutants with GA led toswollen fruit but no mature seeds. “These results indicated that JA signalling is required forstamen development and is independent of the stimulation of GA signalling, even though

PAGE 2GA could partially compensate for a lack of JA function during floral development,” state
the researchers in their report.
The researchers conclude that GTR1/NPF2.10 is a multifunctional transporter for abioactive form of JA, GA and glucosinolates – a class of organic compound derived fromglucose and amino acid. The results also suggest that GTR1/NPF2.10 plays an importantrole in stamen development and fertility and may also be important for hormone transportin vegetative tissue.

BackgroundArabidopsis
The researchers used Arabidopsis – a small flowering plant related to cabbage and mustard– as the focus of their research. There are many different types of Arabidopsis including
Arabidopsis thaliana – the type used in the current study, otherwise known as Thale cress–is considered to be a model organism. Changes in the plant are easily noticeable so it isoften used in biological research. It was also the first organism to have its full genome
sequenced.
Arabidopsis proliferates through sexual reproduction, requiring fusion between female andmale gametes so that the genes passed to the next generation combine those fromdifferent parent plants. This fusion takes place through pollination, where pollen from themale stamens - which develops the male gamete - makes contact with the seeds in thefemale part of the plant, the ovule.
The role of JA and GA
Jasmonates (JA) and gibberellins (GA) are two types of hormones that have been noted fortheir potential significance in seed germination, flowering and development. Plant JAs are
hormones derived from a type of acid and regulate several plant processes from pollen andstamen maturation, aging and responses in defence against both other organisms andenvironmental factors. JA-deficient Arabidopsis plants are prone to filament elongation
defects and incomplete flowering and pollen release, making them male sterile.
GA regulates stamen development and is required for flowering, seed germination, rootand shoot growth and development of the seeds and seed capsule (or fruit). Male sterility
in certain GA mutants has also been attributed to defective, that is, arrested stamen
filament elongation. While previous studies suggest the existence of cross talk between thetwo types of hormones, the functional role of the interplay in flower development has so far
not been identified.
Identification of GTR1
The researchers identified the significance of GTR1 in JA mediated processes by analysing
genes co-expressed with nine different types of JA biosynthetic genes. The analysis
revealed a unique gene, AT3G47960/GTR1/NPF2.10, which encodes a glucosinolatetransporter. The gene belongs to the NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTERFAMILY (NPF). Other NPF genes have been found responsible for the transport of auxin (aPAGE 3growth hormone) abscisic acid (ABA) which functions in many developmental processes
including dormancy, as well as GA. This led to the initial hypothesis that GTR1/NPF2.10
may be responsible for the transport of JA or other hormones.

Figure image and caption

Figure caption: gtr1 phenotypes in flower. (a) The gtr1 mutant exhibited decreased seedproduction. The top panel shows representative primary flowering. The bottom panel
shows representative seed capsules or fruit. Scale bar: 10 mm. (b) The gtr1 had shorter
stamen filaments than the WT and failed in anther dehiscence. Scale bar: 0.5mm.

ReferenceAuthors:

Hikaru Saito, Takaya Oikawa, Shin Hamamoto, Yasuhiro Ishimaru, Miyu
Kanamori-Sato, Yuko Sasaki-Sekimoto, Tomoya Utsumi, Jing Chen, Yuri
Kanno, Shinji Masuda, Yuji Kamiya, Mitsunori Seo, Nobuyuki Uozumi,
Minoru Ueda and Hiroyuki Ohta
Title of Original Paper: The jasmonate-responsive GTR1 transporter is required forgibberellin-mediated stamen development in Arabidopsis
Journal:Nature Communications 6
DOI:
10.1038/ncomms7095