# Plant Synthetic Promoters
## 2 Sections of Plant Promoters  
### Core Promoter  
Studies on the _Arabidopsis thaliana_ genome suggest that, in plants, the promoters of complex transcriptional regulation, which are common in the stress-responsive genes, tend to be longer (1672 bp) than other genes that respond to fewer signals (1113 bp) [80]. This could be explained by the relative austerity of cis-active motifs, and lower space requirement to gather them into promoters which reply to limited stimuli. The segment of the promoter localized at approximately 50-100 bp upstream and downstream from the transcription start site (TSS) is recognized as a core or minimal promoter, where transcription initiation occurs (Figure 1) [81]. The first core promoter component identified in the SV40 early region is the TATAbox [82]. Such elements are localized approximately 32 bp upstream from the transcription start site (TSS) in plant genes (Figure 1) [83; 84]. While the distribution of the TATAbox is species-specific, in most cases it is found around \(\sim\)30 bp upstream of the TSS. In sorghum, the peak was found \(\sim\)40 bp upstream of the TSS, with an additional lower peak at \(\sim\)30 bp upstream of the TSS. In the maize genome, two additional peaks of TATA-box localization were observed at \(\sim\)55 and \(\sim\)70 bp upstream of the TSS. Core promoters containing a TATA-box were up to fourfold more active than those without TATA, particularly when the TATA-box is found 23 to 59 bp upstream of the TSS. Therefore, increasing the distance from TATA-box to the TSS decreases the strength of maize promoters [85]. The consensus sequence of TATA-box in plants is TATAWAW (W = A/T) [86]. However, computational analyses of 79 plant promoters suggest that the TATA-box consensus sequence is TCACTATATATAG [87]. The TATA-box is bound by a subunit of TFIID known as TATA-box binding protein (TBP), enabling the assembly of the RNA polymerase II preinitiation complex [81; 88]. The relative stability of TATA-box localization in relation to the TSS, combined with the information of interacting proteins, distinguishes TATA-box from other regulatory DNA sequences in the core promoter. The importance of the TATA-box sequence for proper gene expression regulation was confirmed by [PERSON] et al. [89]. The authors used PCR and specific primers to introduce single nucleotide substitutions to the TATA-box of the CaMV35S promoter. Two obtained variants, A4T and T5A, showed, respectively, 1.2- and 1.1-fold higher activity in plant  
Figure 1: Structure of the plant core, proximal, entire promoter, and enhancer. Localization of representative cis-active motifs is provided together with corresponding trans-factors. protoplasts as compared to the wild-type TATA-box sequence. Moreover, eight mutants (T1G, A4C, A4G, T5A, A6G, A7C, A7G, and A7T) presented a similar or higher activity to the wild-type TATA-box [89]. The TATA box is required not only for accurate transcription initiation but also to determine the level and selectivity of gene expression in plants [90; 91; 92]. [PERSON] et al. found that among 12,749 tested dicot _A. thaliana_ genes, only approximately 29% indicated a TATA-box, as did only 19% of monocot _Oryza sativa_ genes [83; 93]. The common lack of TATA-box in plant core promoters suggests its putative functional substitution by other core promoter elements as Inr or Y patch, supporting the correct DNA-protein interaction during RNA polymerase II preinitiation complex formation [85; 90]. Moreover, TATA-box genes are less frequently found among those present in EST databases and have shorter 5\({}^{\prime}\)UTRs (108 bp) than TATA-less promoters (138 bp), lacking the TATA-box element [83]. The presence of a TATA-box is also common in gene promoters regulated by light or biotic and abiotic stress [92; 94]. Nucleotide frequency matrices within TSS in dicot and monocot plants and different promoters were described by [PERSON] et al. [95].