Physiological, anatomical and transcriptional alterations in a rice mutant leading to enhanced water stress tolerance

• Published in: AoB plants 2015-03, Vol.7, p.plv023
• Main Authors: 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.
• Format: Article
• Language: English
• Subjects: Cactus; Cavitation; Gene expression; Morphology; Physiology; Plant growth; Polyethylene glycol
• ISSN: 2041-2851; 2041-2851
• DOI: 10.1093/aobpla/plv023

Water stress is a serious challenge to rice production. Understanding water stress tolerance is essential for precise trait modification. We identified an EMS induced mutant showing enhanced tolerance to water deficit stress at the vegetative stage. Multiple alterations in physiological behaviour, root morphological and anatomical structure, stomatal response and gene expression in various signalling pathways were found to be responsible for increased tolerance in the mutant. The mutant will be useful for dissecting the water stress tolerance mechanism in rice. Abstract 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 it