Metabolite and Phytohormone Profiling Illustrates Metabolic Reprogramming as an Escape Strategy of Deepwater Rice during Partially Submerged Stress.

Atsushi Fukushima,Motoyuki Ashikari,Tomoko Nishizawa,Miyako Kusano,Yoko Hattori,Yoshinori Utsumi,Motoaki Seki,Makoto Kobayashi,Hitoshi Sakakibara,Akira Oikawa,Takeshi Kuroha,Keisuke Nagai,Kazuki Saito,Mikiko Kojima

doi:10.3390/metabo10020068

Abstract

Rice varieties that can survive under submergence conditions respond to flooding either by enhancing internode elongation or by quiescence of shoot elongation. Despite extensive efforts to identify key metabolites triggered by complete submergence of rice possessing SUBMERGENCE 1 (SUB1) locus, metabolic responses of internode elongation of deepwater rice governed by the SNORKEL 1 and 2 genes remain elusive. This study investigated specific metabolomic responses under partial submergence (PS) to deepwater- (C9285) and non-deepwater rice cultivars (Taichung 65 (T65)). In addition, we examined the response in a near-isogenic line (NIL-12) that has a C9285 genomic fragment on chromosome 12 introgressed into the genetic background of T65. Under short-term submergence (0–24 h), metabolite profiles of C9285, NIL-12, and T65 were compared to extract significantly changed metabolites in deepwater rice under PS conditions. Comprehensive metabolite and phytohormone profiling revealed increases in metabolite levels in the glycolysis pathway in NIL-12 plants. Under long-term submergence (0–288 h), we found decreased amino acid levels. These metabolomic changes were opposite when compared to those in flood-tolerant rice with SUB1 locus. Auxin conjugate levels related to stress response decreased in NIL-12 lines relative to T65. Our analysis helped clarify the complex metabolic reprogramming in deepwater rice as an escape strategy.

Highlights

Flooding is an environmental stress that affects plant growth and development
To investigate the relationship among rapid internode elongation, energy source, and changes in metabolite levels, we first focused on deepwater rice C9285 under different light and different submergence conditions (Supplementary Figures S1 and S2)
We evaluated growth and amount of chlorophyll in leaf tissue at 2, 4, 6, and 10 days after the four submergence treatments (Figure 1)

Summary

Introduction

Flooding is an environmental stress that affects plant growth and development. Most irrigated rice (Oryza sativa) cultivars are not capable of dealing with flooding. It is known that flood-tolerant rice cultivars have developed two opposing adaptation mechanisms to tolerate flooding: ‘escape strategy’. The flash-flood-tolerant rice plants that adapted a ‘quiescence strategy’. Flood-tolerant rice using an ‘escape strategy’ can tolerate deepwater flooding conditions, such as partial submergence (PS), by rapidly elongating their internodes when water levels rise [2,6]. Many studies on Arabidopsis (for example, see [5]), Oryza (for example, see [7,8]), Rumex [9,10,11,12], Rorippa [3,13,14], and Echinochloa [15,16] have investigated the molecular mechanisms for withstanding flooding

Methods

Results

Discussion

Conclusion