Lima John Milton, Nath Manoj, Dokku Prasad, Raman K V, Kulkarni K P, Vishwakarma C, Sahoo S P, Mohapatra U B, Mithra S V Amitha, Chinnusamy V, Robin S, Sarla N, Seshashayee M, Singh K, Singh A K, Singh N K, Sharma R P, Mohapatra T
National Research Centre on Plant Biotechnology, IARI, New Delhi, India Department of Botany, North Orissa University, Baripada, Odisha, India.
National Research Centre on Plant Biotechnology, IARI, New Delhi, India.
AoB Plants. 2015 Mar 27;7:plv023. doi: 10.1093/aobpla/plv023.
Water stress is one of the most severe constraints to crop productivity. Plants display a variety of physiological and biochemical responses both at the cellular and whole organism level upon sensing water stress. Leaf rolling, stomatal closure, deeper root penetration, higher relative water content (RWC) and better osmotic adjustment are some of the mechanisms that plants employ to overcome water stress. In the current study, we report a mutant, enhanced water stress tolerant1 (ewst1) with enhanced water stress tolerance, identified from the ethyl methanesulfonate-induced mutant population of rice variety Nagina22 by field screening followed by withdrawal of irrigation in pots and hydroponics (PEG 6000). Though ewst1 was morphologically similar to the wild type (WT) for 35 of the 38 morphological descriptors (except chalky endosperm/expression of white core, decorticated grain colour and grain weight), it showed enhanced germination in polyethylene glycol-infused medium. It exhibited increase in maximum root length without any significant changes in its root weight, root volume and total root number on crown when compared with the WT under stress in PVC tube experiment. It also showed better performance for various physiological parameters such as RWC, cell membrane stability and chlorophyll concentration upon water stress in a pot experiment. Root anatomy and stomatal microscopic studies revealed changes in the number of xylem and phloem cells, size of central meta-xylem and number of closed stomata in ewst1. Comparative genome-wide transcriptome analysis identified genes related to exocytosis, secondary metabolites, tryptophan biosynthesis, protein phosphorylation and other signalling pathways to be playing a role in enhanced response to water stress in ewst1. The possible involvement of a candidate gene with respect to the observed morpho-physiological and transcriptional changes and its role in stress tolerance are discussed. The mutant identified and characterized in this study will be useful for further dissection of water stress tolerance in rice.
水分胁迫是作物生产力面临的最严重限制因素之一。植物在感知水分胁迫时，会在细胞和整个生物体水平上表现出多种生理和生化反应。叶片卷曲、气孔关闭、根系更深扎、相对含水量（RWC）更高以及更好的渗透调节是植物用来克服水分胁迫的一些机制。在本研究中，我们报道了一个水分胁迫耐受性增强的突变体，即增强型水分胁迫耐受性1（ewst1），它是通过田间筛选，随后在盆栽和水培（PEG 6000）中停止灌溉，从水稻品种Nagina22的甲基磺酸乙酯诱导突变群体中鉴定出来的。尽管ewst1在38个形态学描述符中的35个方面与野生型（WT）形态相似（除粉质胚乳/白芯表达、脱壳谷粒颜色和粒重外），但它在聚乙二醇灌注培养基中发芽率更高。在PVC管试验中，与胁迫条件下的WT相比，它的最大根长增加，而根重、根体积和冠部总根数没有显著变化。在盆栽试验中，水分胁迫时，它在各种生理参数如RWC、细胞膜稳定性和叶绿素浓度方面也表现更好。根解剖和气孔显微镜研究揭示了ewst1中木质部和韧皮部细胞数量、中央后生木质部大小和关闭气孔数量的变化。全基因组转录组比较分析确定了与胞吐作用、次生代谢产物、色氨酸生物合成、蛋白质磷酸化和其他信号通路相关的基因在ewst1对水分胁迫的增强反应中发挥作用。讨论了一个候选基因与观察到的形态生理和转录变化的可能关联及其在胁迫耐受性中的作用。本研究中鉴定和表征的突变体将有助于进一步剖析水稻的水分胁迫耐受性。
