Osmotic Stress Leads to Significant Changes in Rice Root Metabolic Profiles between Tolerant and Sensitive Genotypes.

Maya Matsunami,Natsumi Kimura,Atsushi Ogawa,Kyoko Toyofuku

doi:10.3390/plants9111503

Maya Matsunami, Natsumi Kimura + Show 2 more

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https://doi.org/10.3390/plants9111503

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Abstract

To breed osmotic stress-tolerant rice, the mechanisms involved in maintaining root growth under osmotic stress is important to elucidate. In this study, two rice (Oryza sativa L.) cultivars, IR 58 (stress-tolerant cultivar) and Basilanon (stress-sensitive cultivar), were used. After 1, 3, and 7 days of −0.42 MPa osmotic stress treatment induced by polyethylene glycol (PEG) 6000, root metabolomes were analyzed, yielding 276 detected compounds. Among 276 metabolites, 102 metabolites increased with the duration of the stress treatment in IR 58 roots, and only nine metabolites decreased. In contrast, 51 metabolites increased, and 45 metabolites decreased in Basilanon roots. Principal component analysis (PCA) scores clearly indicated differences between the cultivars and the treatments. Pathway analysis showed that the metabolites exhibiting stress-induced increases in IR 58 were those involved in sugar metabolism (such as sucrose 6’-phosphate, glucose 1-phosphate), polyamine and phenylpropanoid metabolisms (such as spermine, spermidine, gamma-aminobutyric acid (GABA)), and glutathione metabolism (such as glutathione, cysteine, cadaverine). IR 58 roots showed an increase in the most proteinogenic amino acids such as proline, serine, glutamine and asparagine. It was also maintained or increased the tricarboxylic acid (TCA) cycle intermediates (citric acid, cis-Aconitic acid, isocitric acid, fumaric acid, malic acid) under osmotic stress compared with that under control. Therefore, IR 58 actively synthesized various metabolites, and the increase in these metabolites contributed to the maintenance of important biological functions such as energy production and antioxidant defense to promote root development under osmotic stress.

Highlights

Rice is the world’s most important food crop and a primary food source for more than half of the world’s population [1]
Sucrose content as a respiratory substrate greatly increased in the IR 58 roots under stress (Table 1)
The target of the sorghum study was leaf gamma-aminobutyric acid (GABA) content, our root study shows the significant increase in GABA only in the tolerant cultivar, suggesting that the increase in GABA in the plant body was effective as a characteristic of the stress-tolerant genotypes

Summary

Introduction

Rice is the world’s most important food crop and a primary food source for more than half of the world’s population [1]. More than 90% of the world’s rice is grown and consumed in Asia, where 60%. Rice accounts for 35%–60% of the calories consumed by 3 billion Asians. Osmotic stress (drought stress and salt stress) is the most important abiotic stress for rice production. Water deficits commonly occur in rain-fed rice production areas, which account for about half of the total rice production area globally [2]. Rice productivity in rain-fed ecosystems is lower than that under irrigated cultivation because of the high sensitivity of rice to drought [3]. Further genetic improvement, in addition to novel production technologies, is required for sustainable rice production

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