Molecular Characterization and Expression Profiling of Tomato GRF Transcription Factor Family Genes in Response to Abiotic Stresses and Phytohormones

Abstract

Growth regulating factors (GRFs) are plant-specific transcription factors that are involved in diverse biological and physiological processes, such as growth, development and stress and hormone responses. However, the roles of GRFs in vegetative and reproductive growth, development and stress responses in tomato (Solanum lycopersicum) have not been extensively explored. In this study, we characterized the 13 SlGRF genes. In silico analysis of protein motif organization, intron–exon distribution, and phylogenetic classification confirmed the presence of GRF proteins in tomato. The tissue-specific expression analysis revealed that most of the SlGRF genes were preferentially expressed in young and growing tissues such as flower buds and meristems, suggesting that SlGRFs are important during growth and development of these tissues. Some of the SlGRF genes were preferentially expressed in fruits at distinct developmental stages suggesting their involvement in fruit development and the ripening process. The strong and differential expression of different SlGRFs under NaCl, drought, heat, cold, abscisic acid (ABA), and jasmonic acid (JA) treatment, predict possible functions for these genes in stress responses in addition to their growth regulatory functions. Further, differential expression of SlGRF genes upon gibberellic acid (GA3) treatment indicates their probable function in flower development and stress responses through a gibberellic acid (GA)-mediated pathway. The results of this study provide a basis for further functional analysis and characterization of this important gene family in tomato.

Characterization and expression analysis of growth regulating factor (GRF) family genes in cucumber

“…As shown in Fig. 1A, the Q-L-Q residues were highly conserved in nearly all the GRF proteins from cucumber, Arabidopsis and rice, with the exception of AtGRF9, which contained F in place of L. This phenomenon was also observed in the GRF proteins of Solanum lycopersicum [12] and Camellia sinensis [11]. A zinc finger motif (CCCH) was present within the WRC domain in all CsGRF, AtGRF and OsGRF proteins.…”

“…In this study, we conducted a comprehensive analysis of the GRF family genes in cucumber and we identified 8 CsGRFs. The number of GRFs was smaller than that in some other plant species, such as Arabidopsis (9 members) [2], citrus (9 members) [8], pear (9 members) [7], rice (12 members) [3], tomato (13 members) [12], maize (14 members) [4], whereas it was larger than that in tea plant (6 members) [11]. This phenomenon may be attributed to gene duplication events of the GRF gene family.…”

“…GRFs are plant-specific transcription factors (TFs) widely distributed in the genomes of all known seed plants [1]. In previous studies, GRF family genes were identified in different plant species, such as Arabidopsis [2], rice [3], maize [4], Chinese cabbage [5], cucumber, melon and watermelon [6], Chinese pear, poplar and grape [7], citrus [8], common bean [9], oilseed rape [10], tea plant [11], and tomato [12]. These reports showed that all of the GRF proteins harbor two types of N-terminal domains, named QLQ (Gln, Leu, Gln) and WRC (Trp, Arg, Cys).…”

“…The WRC domain contains a nuclear localization signal and a zinc finger DNA binding motif, which is capable of binding to DNA [2,15]. In addition, some GRF proteins also contain less-conserved TQL (Thr, Gln, Leu), FFD (Phe, Phe, Asp) and GGPL (Gly, Gly, Pro, Leu) domains in their C-terminal regions [9,11,12].…”

“…GRF proteins also function in responses to various abiotic stress conditions such as salt, drought, heat and cold [12,30]; however, the roles of plant GRF family genes in stress responses remain elusive. Although a previous study reported 8 GRF family genes in cucumber [6], to date there has been no report about the molecular and expression characterization of the cucumber GRF gene family.…”