State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, PR China.
BMC Plant Biol. 2012 Aug 12;12:144. doi: 10.1186/1471-2229-12-144.
As a large family of regulatory proteins, WRKY transcription factors play essential roles in the processes of adaptation to diverse environmental stresses and plant growth and development. Although several studies have investigated the role of WRKY transcription factors during these processes, the mechanisms underlying the function of WRKY members need to be further explored, and research focusing on the WRKY family in cotton crops is extremely limited.
In the present study, a gene encoding a putative WRKY family member, GhWRKY15, was isolated from cotton. GhWRKY15 is present as a single copy gene, and a transient expression analysis indicated that GhWRKY15 was localised to the nucleus. Additionally, a group of cis-acting elements associated with the response to environmental stress and plant growth and development were detected in the promoter. Consistently, northern blot analysis showed that GhWRKY15 expression was significantly induced in cotton seedlings following fungal infection or treatment with salicylic acid, methyl jasmonate or methyl viologen. Furthermore, GhWRKY15-overexpressing tobacco exhibited more resistance to viral and fungal infections compared with wild-type tobacco. The GhWRKY15-overexpressing tobacco also exhibited increased RNA expression of several pathogen-related genes, NONEXPRESSOR OF PR1, and two genes that encode enzymes involved in ET biosynthesis. Importantly, increased activity of the antioxidant enzymes POD and APX during infection and enhanced expression of NtAPX1 and NtGPX in transgenic tobacco following methyl viologen treatment were observed. Moreover, GhWRKY15 transcription was greater in the roots and stems compared with the expression in the cotyledon of cotton, and the stems of transgenic plants displayed faster elongation at the earlier shooting stages compared with wide type tobacco. Additionally, exposure to abiotic stresses, including cold, wounding and drought, resulted in the accumulation of GhWRKY15 transcripts.
Overall, our data suggest that overexpression of GhWRKY15 may contribute to the alteration of defence resistance to both viral and fungal infections, probably through regulating the ROS system via multiple signalling pathways in tobacco. It is intriguing that GhWRKY15 overexpression in tobacco affects plant growth and development, especially stem elongation. This finding suggests that the role of the WRKY proteins in disease resistance may be closely related to their function in regulating plant growth and development.
WRKY 转录因子作为一个庞大的调控蛋白家族，在植物适应各种环境胁迫、生长和发育过程中发挥着重要作用。尽管已有多项研究探讨了 WRKY 转录因子在这些过程中的作用，但 WRKY 成员功能的机制仍需进一步探索，而且棉花作物中 WRKY 家族的研究极为有限。
本研究从棉花中分离出一个编码假定 WRKY 家族成员的基因 GhWRKY15。GhWRKY15 是一个单拷贝基因，瞬时表达分析表明 GhWRKY15 定位于细胞核。此外，在启动子中检测到与环境胁迫和植物生长发育相关的一组顺式作用元件。Northern blot 分析显示，GhWRKY15 在棉花幼苗受到真菌侵染或水杨酸、茉莉酸甲酯或甲基紫精处理后表达明显上调。此外，与野生型烟草相比，GhWRKY15 过表达的烟草对病毒和真菌的感染表现出更强的抗性。GhWRKY15 过表达的烟草还表现出几种与病原体相关基因（PR1 非表达基因）和两个参与 ET 生物合成的酶基因的 RNA 表达增加。重要的是，在感染过程中观察到抗氧化酶 POD 和 APX 的活性增加，以及在甲基紫精处理后转基因烟草中 NtAPX1 和 NtGPX 的表达增强。此外，GhWRKY15 在棉花的根和茎中的转录水平高于子叶中的表达，并且在早期抽薹阶段，转基因植物的茎比野生型烟草生长得更快。此外，冷、伤和干旱等非生物胁迫导致 GhWRKY15 转录本的积累。
总体而言，我们的数据表明，GhWRKY15 的过表达可能通过多条信号通路调节 ROS 系统，从而导致烟草对病毒和真菌感染的防御抗性发生改变。有趣的是，GhWRKY15 在烟草中的过表达影响植物的生长和发育，特别是茎的伸长。这一发现表明，WRKY 蛋白在抗病性中的作用可能与其在调节植物生长和发育中的功能密切相关。
