Genetic strategies can be effective in improving wheat (Triticum aestivum L.) drought stress tolerance, but accumulating evidence suggests that overexpressing drought-resistance genes, especially genes related to the abscisic acid (ABA) signaling pathway, can retard plant growth. We previously characterized the positive roles of the wheat bZIP transcription factor TaFD-Like2-1A (TaFDL2-1A) in drought stress tolerance and ABA biosynthesis and response, whereas a dwarfing shoot exhibited under normal conditions. This study determined the underlying mechanisms that allow TaFDL2-1A to affect shoot growth. Overexpressing TaFDL2-1A decreased cell length, cell width, leaf size, shoot length, and biomass in wheat. The results of RNA-seq showed that multiple differently expressed transcripts are enriched in the auxin signaling pathway. Further analysis indicated higher expression levels of Gretchen Hagen3 (GH3) genes and lower indole-3-acetic acid (IAA) concentrations in the TaFDL2-1A overexpression lines. Exogenous IAA treatment restored the phenotypes of the TaFDL2-1A overexpression lines to wild-type levels. Transcriptional regulation analysis suggested that TaFDL2-1A enhances the expression of auxin metabolism genes, such as TaGH3.2-3A, TaGH3.2-3B, TaGH3.8-2A, and TaGH3.8-2D, by directly binding to ACGT core cis-elements. Furthermore, tafdl2 knock-out plants had lower expression levels of these GH3 genes and higher IAA levels than Fielder wheat. These GH3 gene expression and IAA levels were induced and reduced in Fielder wheat and tafdl2 knock-out plants treated with exogenous ABA. Our findings elucidate mechanisms underlying the functional redundancy of TaFDL2-1A in the crosstalk between ABA and IAA to affect shoot growth and provide insights into the balance between drought resistance and yield in wheat.

中文翻译：

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转录因子 TaFDL2-1A 在脱落酸介导的生长素代谢中发挥作用，调节小麦芽的生长


遗传策略可以有效提高小麦 （Triticum aestivum L.） 的耐旱性，但越来越多的证据表明，过表达抗旱基因，尤其是与脱落酸 （ABA） 信号通路相关的基因，会延缓植物生长。我们之前表征了小麦 bZIP 转录因子 TaFD-Like2-1A （TaFDL2-1A） 在耐旱胁迫和 ABA 生物合成和响应中的积极作用，而在正常条件下表现出矮化芽。本研究确定了允许 TaFDL2-1A 影响芽生长的潜在机制。过表达 TaFDL2-1A 降低了小麦的细胞长度、细胞宽度、叶大小、地上部长度和生物量。RNA-seq 结果显示，多个不同表达的转录本在生长素信号通路中富集。进一步分析表明，TaFDL2-1A 过表达系中 Gretchen Hagen3 （GH3） 基因的表达水平较高，吲哚-3-乙酸 （IAA） 浓度较低。外源 IAA 处理将 TaFDL2-1A 过表达系的表型恢复到野生型水平。转录调控分析表明，TaFDL2-1A 通过直接结合 ACGT 核心顺式元件，增强生长素代谢基因如 TaGH3.2-3A、TaGH3.2-3B、TaGH3.8-2A 和 TaGH3.8-2D 的表达。此外，与 Fielder 小麦相比，tafdl2 敲除植株的这些 GH3 基因的表达水平较低，IAA 水平较高。这些 GH3 基因表达和 IAA 水平在外源 ABA 处理的 Fielder 小麦和 tafdl2 敲除植物中被诱导和降低。 我们的研究结果阐明了 ABA 和 IAA 之间串扰中 TaFDL2-1A 功能冗余影响芽生长的机制，并为小麦抗旱性和产量之间的平衡提供了见解。