Transcriptional regulation of SlPYL, SlPP2C, and SlSnRK2 gene families encoding ABA signal core components during tomato fruit development and drought stress

Abstract

In order to characterize the potential transcriptional regulation of core components of abscisic acid (ABA) signal transduction in tomato fruit development and drought stress, eight SlPYL (ABA receptor), seven SlPP2C (type 2C protein phosphatase), and eight SlSnRK2 (subfamily 2 of SNF1-related kinases) full-length cDNA sequences were isolated from the tomato nucleotide database of NCBI GenBank. All SlPYL, SlPP2C, and SlSnRK2 genes obtained are homologous to Arabidopsis AtPYL, AtPP2C, and AtSnRK2 genes, respectively. Based on phylogenetic analysis, SlPYLs and SlSnRK2s were clustered into three subfamilies/subclasses, and all SlPP2Cs belonged to PP2C group A. Within the SlPYL gene family, SlPYL1, SlPYL2, SlPYL3, and SlPYL6 were the major genes involved in the regulation of fruit development. Among them, SlPYL1 and SlPYL2 were expressed at high levels throughout the process of fruit development and ripening; SlPYL3 was strongly expressed at the immature green (IM) and mature green (MG) stages, while SlPYL6 was expressed strongly at the IM and red ripe (RR) stages. Within the SlPP2C gene family, the expression of SlPP2C, SlPP2C3, and SlPP2C4 increased after the MG stage; SlPP2C1 and SlPP2C5 peaked at the B3 stage, while SlPP2C2 and SlPP2C6 changed little during fruit development. Within the SlSnRK2 gene family, the expression of SlSnRK2.2, SlSnRK2.3, SlSnRK2.4, and SlSnRK2C was higher than that of other members during fruit development. Additionally, most SlPYL genes were down-regulated, while most SlPP2C and SlSnRK2 genes were up-regulated by dehydration in tomato leaf.

Fundamental and applied research in ABA signaling: Regulation by ABA of the chromatin remodeling ATPase BRAHMA and biotechnological use of the PP2CA promoter.

“…Since the discovery of Arabidopsis PYR/PYL/RCAR receptors, several orthologous genes had been discovered in important crops as tomato, rice, strawberry and soybean (Sun et al, 2011, Chai et al, 2011, Kim et al, 2012, Bai et al, ! 28 2013.…”

ABA-deficiency and molecular mechanisms involved in the dehydration response and ripening of citrus fruit

“…Seiler et al (2011) found that development of barley grain under drought was ABA-controlled through PYL/PP2CA-mediated activation of the ABI5 transcription factor. Sun et al (2011) performed a transcriptional study in which the relationship between ABA and the PP2CAs gene-regulation was highlighted in different organs, developmental stages and in response to water stress. Studies performed in grape identified six putative PP2CAs and revealed that their expressions in leaves and roots were highly regulated by abiotic ABAincreasing stresses such as high salt concentration, cold and drought (Boneh et al, 2012a;Boneh et al, 2012b), and that sugar and exogenous ABA regulated these and other ABA-signalling genes during ripening of this non-climacteric fruit (Gambetta et al, 2011).…”

“…The group of SnRK2 is composed of 10 plant-specific proteins, which present a characteristic D-rich C-terminal domain that is essential for transducing the ABA signal (Yoshida et al, 2006a (Sun et al, 2011;Boneh et al, 2012a).…”

“…Nevertheless, several reports have already analyzed the expression pattern of these genes in tomato fruits (Sun et al, 2011) and in grape (Boneh et al, 2012a). Results obtained in tomato fruit showed that SnRK2s were transiently induced by exogenous ABA and highly expressed at the most immature stages, concomitantly with lowest endogenous ABA levels (Sun et al, 2011).…”

“…The PYR/PYL/RCAR protein structures consist of a central seven-stranded β-sheet flanked by two α-helixes highly conserved among species (Ma et al, 2009;Santiago et al, 2009b;Chai et al, 2011;Sun et al, 2011;Kim et al, 2012). This β-sheet produces a cavity that contains a ligand-binding pocket that closes after ABA binding through conformational changes of two conserved β-loops that serve as gate and latch (Park et al, 2009;Ma et al, 2009;Melcher et al, 2009;Santiago et al, 2012).…”