Abstract
BackgroundERF transcription factors (TFs) belong to the Apetala2/Ethylene responsive Factor (AP2/ERF) TF family and play a vital role in plant growth and development processes. Capsorubin and capsaicinoids have relatively high economic and nutritional value, and they are specifically found in Capsicum. However, there is little understanding of how ERFs participate in the regulatory networks of capsorubin and capsaicinoids biosynthesis.ResultsIn this study, a total of 142 ERFs were identified in the Capsicum annuum genome. Subsequent phylogenetic analysis allowed us to divide ERFs into DREB (dehydration responsive element binding proteins) and ERF subfamilies, and further classify them into 11 groups with several subgroups. Expression analysis of biosynthetic pathway genes and CaERFs facilitated the identification of candidate genes related to the regulation of capsorubin and capsaicinoids biosynthesis; the candidates were focused in cluster C9 and cluster C10, as well as cluster L3 and cluster L4, respectively. The expression patterns of CaERF82, CaERF97, CaERF66, CaERF107 and CaERF101, which were found in cluster C9 and cluster C10, were consistent with those of accumulating of carotenoids (β-carotene, zeaxanthin and capsorubin) in the pericarp. In cluster L3 and cluster L4, the expression patterns of CaERF102, CaERF53, CaERF111 and CaERF92 were similar to those of the accumulating capsaicinoids. Furthermore, CaERF92, CaERF102 and CaERF111 were found to be potentially involved in temperature-mediated capsaicinoids biosynthesis.ConclusionThis study will provide an extremely useful foundation for the study of candidate ERFs in the regulation of carotenoids and capsaicinoids biosynthesis in peppers.
Highlights
ERF transcription factors (TFs) belong to the Apetala2/Ethylene responsive Factor (AP2/ERF) TF family and play a vital role in plant growth and development processes
The ERF subfamily typically binds to the GCC-box in the promoter regions, whereas the Dehydration responsive element binding proteins (DREB) subfamily is characterized by dehydration-responsive element binding factor containing a core motif of CCGAC [29, 42] According to Nakano and Sakuma’s study [15, 16], this DNA-binding specificity is mainly determined by the 14th and 19th amino acids in the AP2 domain (V14 and E19 for the DREB subfamily but A14 and D19 for the ERF subfamily); the DREB subfamily is completely conserved at V15 and E20, and the ERF subfamily is highly conserved at A14 and D19 (Fig. 1)
Conclusion a total of 142 members in the ERF family were identified in the pepper, and they were divided into DREB and ERF subfamilies
Summary
ERF transcription factors (TFs) belong to the Apetala2/Ethylene responsive Factor (AP2/ERF) TF family and play a vital role in plant growth and development processes. Capsorubin and capsaicinoids have relatively high economic and nutritional value, and they are found in Capsicum. Carotenoids pigments and pungency are important, typical characteristics of peppers, and the accumulation of carotenoids pigments affects the intensity of coloration (red, yellow and orange color) in ripe Capsicum fruit. Carotenoids pigments are synthesized in plastids and are generated from the prenyl lipid biosynthesis pathway (Fig. S1A). Capsaicinoids biosynthesis is unique to Capsicum spp., and it is characterized by tissue specificity. Previous studies have reported that more than 23 types of capsaicinoids were found in peppers [8, 9]. Both capsaicin and dihydrocapsaicin were the most abundant capsaicinoids, representing 91% of the total capsacinoids content [10]. The biosynthetic pathway of capsaicinoids consists of two distinct pathways, the phenylalanine and chain fatty acid biosynthesis pathways, which are involved in a series of genes encoding enzymes involved in synthesis, such as Phe ammonialyase (Pal), caffeic acid O-methyltransferase (Comt) and a putative acyltransferase (AT3) (Fig. S1B) [11,12,13]
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