Heterologous expression of rice 9-cis-epoxycarotenoid dioxygenase 4 (OsNCED4) in Arabidopsis confers sugar oversensitivity and drought tolerance

San-Gwang Hwang,Chia-Yun Lee,Ching-Shan Tseng

doi:10.1186/s40529-018-0219-9

San-Gwang Hwang, Chia-Yun Lee + Show 1 more

Open Access

https://doi.org/10.1186/s40529-018-0219-9

Copy DOI

Abstract

BackgroundThe 9-cis-epoxycarotenoid dioxygenases OsNCED4 was cloned from rice in conjunction with OsNCED 1-3 and 5, of which 3 has been shown to function in ABA biosynthesis and alteration of leaf morphology. In higher plants, NCEDs have been shown to be key enzymes controlling ABA biosynthesis and belong to a differentially expressed gene family. Aside from OsNCED3, it remains largely unknown if other OsNCED genes are involved in ABA biosynthesis in rice. Thus, transgenic Arabidopsis plants overexpressing OsNCED4 were generated in the 129B08/nced3 mutant background to explore OsNCED4 function in ABA biosynthesis.ResultsHeterologous expression of OsNCED4 in Arabidopsis increased ABA levels and altered plant size and leaf shape, delayed seed germination, caused sugar oversensitivity in post-germination growth, and enhanced tolerance to drought. The native OsNCED3 and OsNCED4 promoters were expressed in an overlapping pattern in rice seeds and young seedlings, suggesting possible functional redundancy between OsNCED3 and OsNCED4. At the one-leaf stage, similar regulation of OsNCED3 and OsNCED4 gene expression in roots or leaves in response to moderate salt stress (150 mM NaCl) was observed.ConclusionLike OsNCED3, OsNCED4 is functionally active in ABA biosynthesis in rice. OsNCED3 and OsNCED4 might play redundant roles in controlling ABA biosynthesis in rice, as suggested by GUS staining assay, but this should be further analyzed through complementation of rice NCED knockout mutants.

Highlights

The 9-cis-epoxycarotenoid dioxygenases OsNCED4 was cloned from rice in conjunction with OsNCED 1-3 and 5, of which 3 has been shown to function in abscisic acid (ABA) biosynthesis and alteration of leaf morphology
In this study, reverse genetic approaches were used to determine if rice OsNCED4 is functionally active in ABA biosynthesis
Results from GUS staining revealed that both OsNCED3 and OsNCED4 were expressed in roots under both no-salt and salt-stress conditions, the GUS signal appeared to be weaker in the salt-treated roots (Fig. 8b, d)

Summary

Introduction

The 9-cis-epoxycarotenoid dioxygenases OsNCED4 was cloned from rice in conjunction with OsNCED 1-3 and 5, of which 3 has been shown to function in ABA biosynthesis and alteration of leaf morphology. Transgenic Arabidopsis plants overexpressing OsNCED4 were generated in the 129B08/nced mutant background to explore OsNCED4 function in ABA biosynthesis. The functions of abscisic acid (ABA) in regulation of seed dormancy, seedling growth and development, stomatal closure, and stress tolerance is well studied (Jiang and Yu 2009; Zhu et al 2009, 2011; Waterland et al 2010; Gao et al 2011; Bauer et al 2013; Merilo et al 2015). ABA regulates numerous physiological responses in addition to seed germination and seedling growth. The roles of ABA and ABA signaling in plant abiotic stress responses, including drought tolerance, have been recently reviewed and discussed (Sah et al 2016; Vishwakarma et al 2017)

Methods

Results

Discussion

Conclusion