不利的温度会抑制果实的结实，影响产量。我们在非允许的高温条件下分离到一个产番茄突变体的果实，并鉴定其致病基因为 SlHB15A，属于第 iii 类同源结构域亮氨酸拉链转录因子(HD-ZipIII)。SlHB15A 功能缺失突变体显示胚珠发育异常，模拟受精胚珠的转录变化，导致单性结实果实在最佳和非允许温度下，在田间和温室条件下生长。在低温生长条件下，SlHB15A 受条件单一等位基因不足性敏感，并受 microRNA 166(miR166)控制的隐性剂量敏感性。miR166基因敲除 SlHB15A 等位基因，导致与单性结实座果相关的胚珠连续变异。与此相一致的是，含有抗 SlHB15A-miRNA166等位基因的植株发育成正常的胚珠，在低温条件下不能结单性结实。
DNA 亲和纯化测序(DAP-seq)和 RNAseq 分析表明 SlHB15A 是一个双功能转录因子，在胚珠珠被中表达。SlHB15A 与生长素基因的启动子结合，抑制生长素信号传导，并与乙烯基因结合激活其表达。
番茄遗传多样性调查表明，两个历史单性结实突变体 pat 和 pat-1为 SlHB15A 等位基因。我们的发现证明了 SlHB15A 作为一个哨兵的作用，以防止在没有受精的情况下结果，并提供了一种手段，以促进在极端温度下结果。
作者单位：巴黎大学-圣克莱分校
Fruit set is inhibited by adverse temperatures, with consequences on yield. We isolated a tomato mutant producing fruits under non-permissive hot temperatures and identified the causal gene as SlHB15A, belonging to class-III homeodomain leucine-zipper transcription factors (HD-ZipIII). SlHB15A loss-of-function mutants display aberrant ovule development that mimics transcriptional changes occurring in fertilized ovules and leads to parthenocarpic fruit set under optimal and non-permissive temperatures, in field and glasshouse conditions. Under cold growing condition, SlHB15A is subjected to conditional haploinsufficiency and recessive dosage sensitivity controlled by microRNA 166 (miR166). Knockdown of SlHB15A alleles by miR166 leads to a continuum of aberrant ovules correlating with parthenocarpic fruit set. Consistent with this, plants harboring SlHB15A-miRNA166 resistant allele developed normal ovules and were unable to set parthenocarpic fruit under cold condition. DNA affinity purification sequencing (DAP-seq) and RNAseq analyses revealed SlHB15A is a bifunctional transcription factor, expressing in the ovule integument. SlHB15A binds to the promoters of auxin genes to repress auxin signaling and to ethylene genes to activate their expression. Survey of tomato genetic biodiversity identified pat and pat-1, two historical parthenocarpic mutants, as alleles of SlHB15A. Our finding demonstrates the role of SlHB15A as a sentinel to prevent fruit set in the absence of fertilization and provides a mean to enhance fruiting under extreme temperatures.
DOI：10.1016/j.molp.2021.05.005
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