Transcriptional Basis for Differential Thermosensitivity of Seedlings of Various Tomato Genotypes

Abstract

Transcriptional reprograming after the exposure of plants to elevated temperatures is a hallmark of stress response which is required for the manifestation of thermotolerance. Central transcription factors regulate the stress survival and recovery mechanisms and many of the core responses controlled by these factors are well described. In turn, pathways and specific genes contributing to variations in the thermotolerance capacity even among closely related plant genotypes are not well defined. A seedling-based assay was developed to directly compare the growth and transcriptome response to heat stress in four tomato genotypes with contrasting thermotolerance. The conserved and the genotype-specific alterations of mRNA abundance in response to heat stress were monitored after exposure to three different temperatures. The transcripts of the majority of genes behave similarly in all genotypes, including the majority of heat stress transcription factors and heat shock proteins, but also genes involved in photosynthesis and mitochondrial ATP production. In turn, genes involved in hormone and RNA-based regulation, such as auxin- and ethylene-related genes, or transcription factors like HsfA6b, show a differential regulation that associates with the thermotolerance pattern. Our results provide an inventory of genes likely involved in core and genotype-dependent heat stress response mechanisms with putative role in thermotolerance in tomato seedlings.

Transcriptional regulation of HSFA7 and post-transcriptional modulation of HSFB4a by miRNA4200 govern general and varietal thermotolerance in tomato

“…The authors show that intron splicing in wild species results in increased synthesis of an HSFA2 isoform ( HSFA2-II ), implicated in the early stress response, at the expense of HSFA2-I which is involved in the establishment of short-term acclimation and thermotolerance. Recently, a study by Hu et al (2020a) have shown that upon heat stress, the expression of majority of genes behaves similarly in all genotypes, including the HSFs and HSPs, genes involved in photosynthesis and mitochondrial ATP production. In turn, genes involved in hormone and RNA-based regulation, such as auxin- and ethylene-related genes and some transcription factors show a differential regulation that strongly associates with the cultivar thermotolerance pattern (Hu et al 2020a).…”

“…Recently, a study by Hu et al (2020a) have shown that upon heat stress, the expression of majority of genes behaves similarly in all genotypes, including the HSFs and HSPs, genes involved in photosynthesis and mitochondrial ATP production. In turn, genes involved in hormone and RNA-based regulation, such as auxin- and ethylene-related genes and some transcription factors show a differential regulation that strongly associates with the cultivar thermotolerance pattern (Hu et al 2020a). Another recent study by Balyan et al (2020) has shown the orchestration of inherent cultivar-specific transcription factor cascade in regulating the transcription of key genes governing heat tolerance of tolerant tomato cultivar (CLN).…”

“…Despite many conserved features, members of the HSF family show strong diversification of expression patterns and functions within the HSF family (von Koskull-Döring et al 2007; Scharf et al 2012; Xin et al 2019). Along with Arabidopsis, tomato has also been used as a model plant to understand many aspects of HSF-mediated heat stress regulation (Rivero et al 2001; Sato et al 2006; Li et al 2012, Hu et al 2020a, 2020b).…”

“…Heat tolerant and sensitive tomato varieties/genotypes have also been used to understand the naturally evolved signalling mechanisms of acquiring HS-resilience (Frank et al 2009; Bita et al 2011; Balyan et al 2020; Hu et al 2020a). These studies have provided a repertoire of genes involved in core and genotype-dependent HSR mechanisms in tomato.…”

“…These studies have provided a repertoire of genes involved in core and genotype-dependent HSR mechanisms in tomato. While Bita et al (2011) used cDNA-AFLP coupled with microarray analyses in meiotic anther under moderate heat stress, Hu et al (2020a) used seedlings from four genotypes exhibiting different thermotolerance and Balyan et al (2020) performed RNA-seq in leaf from contrasting cultivar pair growing in the Indian sub-continent. Apart from canonical HSR regulators, several novel regulators of heat tolerance like Solyc09g014280 ( Acylsugar acyltransferase ), Solyc07g056570 ( Notabilis ) and Solyc03g020030 ( Pin-II proteinase inhibitor ) were functionally shown to have roles in regulating the variable degree of thermotolerance in contrasting tomato cultivars, the tolerant CLN1621L (henceforth called as CLN) and CA4 (sensitive) (Balyan et al 2020).…”