Key Laboratory of Landscaping Agriculture, Ministry of Agriculture and Rural Affairs/Key Laboratory of Biology of Ornamental Plants in East China, National Forestry and Grassland Administration, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
Jiangsu Graduate Workstation of Nanjing Agricultural University and Nanjing Oriole Island Modern Agricultural Development Co., Ltd., Nanjing, Jiangsu 210043, China.
Plant Cell Physiol. 2022 Nov 22;63(11):1729-1744. doi: 10.1093/pcp/pcac131.
HD-Zip I transcription factors play important roles in plant development and response to abiotic stresses; however, their roles in thermotolerance are largely unknown. Through transcriptome analysis in lily (Lilium longiflorum), we isolated and identified a HD-Zip I gene differentially expressed at high temperatures, LlHB16, which belongs to the β2 subgroup and positively regulates thermotolerance. The expression of LlHB16 was rapidly and continuously activated by heat stress. LlHB16 protein localized to the nucleus and exhibited transactivation activity in both plant and yeast cells, and its C-terminus contributed to its transcriptional activity. Overexpressing LlHB16 in Arabidopsis and lily improved thermotolerance and activated the expression of heat-related genes in both plants, especially that of HSFA2 and MBF1c. In addition, LlHB16 overexpression in Arabidopsis also caused growth defects, delayed flowering and abscisic acid (ABA) insensitivity. Further analysis revealed that LlHB16 directly binds to the promoters of LlHSFA2 and LlMBF1c and activates their expressions. Similarly, the expression of AtHSFA2 and AtMBF1c was also elevated in LlHB16 transgenic Arabidopsis lines. Together, our findings demonstrate that LlHB16 participates in the establishment of thermotolerance involved in activating LlHSFA2 and LlMBF1c, and LlHB16 overexpression resulted in ABA insensitivity in transgenic plants, suggesting that LlHB16 links the basal heat-responsive pathway and ABA signal to collaboratively regulate thermotolerance.
HD-Zip I 转录因子在植物发育和应对非生物胁迫中发挥重要作用；然而，它们在耐热性中的作用在很大程度上是未知的。通过百合（Lilium longiflorum）的转录组分析，我们分离并鉴定了一个在高温下差异表达的 HD-Zip I 基因，LlHB16，它属于β2 亚组，正向调节耐热性。LlHB16 的表达被热胁迫快速且连续地激活。LlHB16 蛋白定位于细胞核，并在植物和酵母细胞中表现出转录激活活性，其 C 端有助于其转录活性。在拟南芥和百合中过表达 LlHB16 提高了耐热性，并激活了这两种植物中与热相关基因的表达，尤其是 HSFA2 和 MBF1c。此外，LlHB16 在拟南芥中的过表达也导致生长缺陷、开花延迟和对脱落酸（ABA）的不敏感。进一步分析表明，LlHB16 直接结合 LlHSFA2 和 LlMBF1c 的启动子并激活它们的表达。同样，LlHB16 转基因拟南芥系中 AtHSFA2 和 AtMBF1c 的表达也升高。总之，我们的研究结果表明，LlHB16 参与了激活 LlHSFA2 和 LlMBF1c 的耐热性的建立，并且 LlHB16 过表达导致转基因植物对 ABA 的不敏感，表明 LlHB16 将基础热响应途径与 ABA 信号联系起来，共同调节耐热性。
