transcriptome of tomato. Characterization of novel regulators for heat stress tolerance in tomato from Indian sub-continent

The footprint of tomato cultivation, a cool region crop that exhibits heat stress (HS) sensitivity, is increasing in the tropics/sub-tropics. Knowledge of novel regulatory hot spots from varieties growing in the Indian sub-continent climatic zones could be vital for developing HS-resilient crops. Comparative transcriptome-wide signatures of a tolerant (CLN1621L) and sensitive (CA4) cultivar pair shortlisted from a pool of varieties exhibiting variable thermo-sensitivity using physiological-, survival- and yield-related traits revealed redundant to cultivar-specific HS regulation. The antagonistically expressing genes encode enzymes and proteins that have roles in plant defence and abiotic stresses. Functional characterization of three antagonistic genes by overexpression and silencing established Solyc09g014280 (Acylsugar acyltransferase) and Solyc07g056570 (Notabilis) that are up-regulated in tolerant cultivar, as positive regulators of HS tolerance and Solyc03g020030 (Pin-II proteinase inhibitor), that are down-regulated in CLN1621L, as negative regulator of thermotolerance. Transcriptional assessment of promoters of these genes by SNPs in stress-responsive cis-elements and promoter swapping experiments in opposite cultivar background showed inherent cultivar-specific orchestration of transcription factors in regulating transcription. Moreover, overexpression of three ethylene response transcription factors (ERF.C1/F4/F5) also improved HS tolerance in tomato. This study identifies several novel HS tolerance genes and provides proof of their utility in tomato thermotolerance.

作为喜凉且对热胁迫（HS）敏感的作物，番茄的种植规模在热带与亚热带地区持续扩张。解析印度次大陆气候区生长的番茄品种中全新的调控热点，对培育耐热胁迫作物至关重要。研究团队通过生理特性、存活率及产量相关性状筛选出一批热敏感性各异的番茄品种群体，从中遴选得到耐热品种CLN1621L与热敏感品种CA4；对二者开展全转录组比较分析后发现，热胁迫的调控模式呈现出从普遍冗余到品种特异性的特征。拮抗表达基因编码参与植物防御与非生物胁迫响应的酶类与蛋白质。通过过表达与基因沉默技术对3个拮抗表达基因开展功能验证，结果证实：在耐热品种中上调表达的Solyc09g014280（酰基糖酰基转移酶，Acylsugar acyltransferase）与Solyc07g056570（Notabilis）为热胁迫耐性的正调控因子；而在CLN1621L中下调表达的Solyc03g020030（Pin-II蛋白酶抑制剂，Pin-II proteinase inhibitor）则为热耐性的负调控因子。通过分析胁迫响应顺式作用元件中的单核苷酸多态性（SNPs）对上述基因的启动子开展转录水平评估，并在相反品种背景中开展启动子互换实验，结果显示转录因子的调控存在固有的品种特异性编排模式。此外，3个乙烯响应转录因子（ERF.C1/F4/F5）的过表达同样可提升番茄的热胁迫耐性。本研究鉴定出多个全新的热胁迫耐性基因，并证实其在番茄热耐性改良中的应用价值。