Ectopic expression of a cytochrome P450 monooxygenase gene PtCYP714A3 from Populus trichocarpa reduces shoot growth and improves tolerance to salt stress in transgenic rice.

Cuiting Wang,Yang Yang,Hongxia Zhang,Xiaojuan Ran,Haihai Wang,Bei Li,Jiantao Zhang

doi:10.1111/pbi.12544

Abstract

SummaryIn Arabidopsis thaliana and Oryza sativa, the cytochrome P450 (CYP) 714 protein family represents a unique group of CYP monooxygenase, which functions as a shoot‐specific regulator in plant development through gibberellin deactivation. Here, we report the functional characterizations of PtCYP714A3, an OsCYP714D1/Eui homologue from Populus trichocarpa. PtCYP714A3 was ubiquitously expressed with the highest transcript level in cambium–phloem tissues, and was greatly induced by salt and osmotic stress in poplar. Subcellular localization analyses indicated that PtCYP714A3‐YFP fusion protein was targeted to endoplasmic reticulum (ER). Expression of PtCYP714A3 in the rice eui mutant could rescue its excessive‐shoot‐growth phenotype. Ectopic expression of PtCYP714A3 in rice led to semi‐dwarfed phenotype with promoted tillering and reduced seed size. Transgenic lines which showed significant expression of PtCYP714A3 also accumulated lower GA level than did the wild‐type (WT) plants. The expression of some GA biosynthesis genes was significantly suppressed in these transgenic plants. Furthermore, transgenic rice plants exhibited enhanced tolerance to salt and maintained more Na+ in both shoot and root tissues under salinity stress. All these results not only suggest a crucial role of PtCYP714A3 in shoot responses to salt toxicity in rice, but also provide a molecular basis for genetic engineering of salt‐tolerant crops.

Highlights

As a class of important plant hormones, gibberellins (GAs) play crucial roles in promoting seed germination, stem elongation, leaf expansion and flower development (Eriksson et al, 2006; King et al, 2001; Ogawa et al, 2003; Schwechheimer, 2008)
The biosynthesis of bioactive GAs such as GA1 and GA4 was initiated from geranylgeranyl diphosphate (GGDP), and catalysed by three types of enzymes including plastid-localized terpene cyclases, membrane-bound cytochrome P450 monooxygenases (P450s) and soluble 2-oxoglutarate-dependent dioxygenases (2ODDs) (Yamaguchi, 2008)
A cytochrome P450 monooxygenase CYP714D1 encoded by Eui gene that was cloned from the recessive tall rice mutant elongated uppermost internode can deactivate non-13-hydroxylated GAs (GA4, GA9 and GA12) by the 16a, 17-epoxidation (Luo et al, 2006; Zhu et al, 2006)

Summary

Introduction

As a class of important plant hormones, gibberellins (GAs) play crucial roles in promoting seed germination, stem elongation, leaf expansion and flower development (Eriksson et al, 2006; King et al, 2001; Ogawa et al, 2003; Schwechheimer, 2008). Using a yeast expression system, CYP714A1 was revealed to be a GAdeactivating enzyme that catalyses the conversion of GA12 to 16carboxylated GA12 (16-carboxy-16b, 17-dihydro GA12), while CYP714A2 acts as a 13-oxidase or 12a-oxidase of GAs or GA precursors depending on the substrate (Nomura et al, 2013). All these reports suggest that CYP714 gene family members from different plant species might have different functions in GA metabolic pathway

Results

Discussion

Conclusion