Targeted Phytohormone Profiling Identifies Potential Regulators of Spikelet Sterility in Rice under Combined Drought and Heat Stress.

Maria Vera Jesus Da Costa,Venkategowda Ramegowda,Sheshshayee Sreeman,Karaba N Nataraja

doi:10.3390/ijms222111690

Maria Vera Jesus Da Costa, Venkategowda Ramegowda + Show 2 more

Open Access

https://doi.org/10.3390/ijms222111690

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Abstract

Rice cultivated under rainfed or semi-irrigated ecosystems is frequently exposed to a combination of drought and heat stress. As a sensitive crop at the reproductive stage, exposure to combined drought and heat stress will have a deleterious effect on yield. In this study, two rice cultivars with contrasting spikelet sterility, AVT2-5315 (low sterility) and AC35027 (high sterility), under combined stress were selected for physiological characterization and phytohormonal profiling at anthesis. Under combined stress, both cultivars did not differ in the physiological parameters such as relative water content, photosynthetic rate, light-adapted chlorophyll fluorescence and biomass, suggesting a similar source activity under stress. However, AVT2-5315 showed better yield due to better pollen and spikelet fertility than AC35027, suggesting its intrinsic tolerance ability under combined stress. Targeted profiling of 15 phytohormones from drought, heat and combined stress-treated flag leaf and spikelet tissues using LC–MS/MS showed increased accumulation of auxins (indole 3-acetic acid and indole 3-butyric acid) in flag leaves and jasmonic acid in spikelets of AVT2-5315, while there was increased accumulation of ethylene in flag leaves and methyl-jasmonate in spikelets of AC35027. Increased accumulation of these hormones correlated with key biosynthetic pathway genes. In the flag leaves, increased accumulation of auxins was correlated with increased transcript levels of YUCCA-like gene 1 (OsYUCCA1) and fish bone (OsFIB), in AVT2-5315 under combined stress. In AC35027, increased ethylene content was correlated with expression of 1-aminocyclopropane-1-carboxylate synthase 1 (OsASC1) and aminocyclopropane-1-carboxylic acid oxidase 2 (OsACO2). Similarly, in spikelets, increased accumulation of jasmonic acid in AVT2-5315 was correlated with expression of allene oxide cyclase (OsAOC) and 12-oxophytodienoic acid reductase 1 (OsOPR1). The mechanism of regulating spikelet sterility by these hormones needs further investigation towards improving rice tolerance to combined stress.

Highlights

Plants under field conditions are routinely exposed to several unpredictable environmental conditions, leading to reduced growth and yield
The weekly maximum temperature ranged from 28–35 ◦ C during the entire growth period (Figure S1a) while during anthesis, the daily maximum temperature ranged from 33–36 ◦ C (Figure S1b)
The results show that combined stress severely affects plant physiological processes, and between drought and heat stress, drought seems to be the dominant stress in the combination

Summary

Introduction

Plants under field conditions are routinely exposed to several unpredictable environmental conditions, leading to reduced growth and yield. Drought and heat stress assume a greater significance due to changing climate and population dynamics. According to the intergovernmental panel on climate change (www.ipcc.ch/2014),the global surface temperature and the amount and pattern of rainfall are likely to become more erratic, subjecting crops to a greater range of environmental stresses. Average temperatures are expected to rise by 2–3 ◦ C over the next. With these inevitable consequences, it is critical to understand the holistic responses of plants under individual drought and heat stresses, and under combined drought and heat stress towards the development of climate-ready crops

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Conclusion