BR deficiency causes increased sensitivity to drought and yield penalty in cotton

Eryong Chen,Xiaoyang Ge,Zuoren Yang,Fuguang Li,Xiaoqian Wang,Chaojun Zhang,Xueyan Zhang

doi:10.1186/s12870-019-1832-9

Abstract

BackgroundBrassinosteroids (BRs) play crucial roles in drought tolerance, but the underlying molecular mechanisms remain unclear in the important oilseed and fiber crop, cotton (Gossypium hirsutum L.).ResultsTo elucidate how BRs mediate drought tolerance in cotton, a cotton brassinosteroid (BR)-deficient mutant, pag1 (pagoda1), was employed for analysis. Importantly, the pag1 mutant showed increased sensitivity to drought stress, with shorter primary roots and fewer lateral roots. The number of stomata was significantly increased in the mutant, and the stomata aperture was much wider than that of the control plants. These mutant plants therefore showed an increased water loss rate. Furthermore, the abscisic acid (ABA) content, photosynthetic efficiency and starch content of the mutant were significantly lower than those of the wild type. The overall performance of the mutant plants was worse than that of the wild-type control under both normal and drought conditions. Moreover, Proteomic analysis revealed reduced levels of stress-related proteins in pag1 plants.ConclusionsThese results suggest that BRs may modulate the drought tolerance of cotton by regulating much genes that related to drought stress and multiple organ responses to drought, including root growth, stomata development, the stomata aperture and photosynthesis. This study provides an important basis for understanding drought resistance regulated by BRs and cultivating drought-resistant cotton lines.

Highlights

Brassinosteroids (BRs) play crucial roles in drought tolerance, but the underlying molecular mechanisms remain unclear in the important oilseed and fiber crop, cotton (Gossypium hirsutum L.)
The pag1 mutant is defective in CS, an active BR In Arabidopsis, BAS1 (CYP734A1) inactivates CS and BL which all belongs to BRs via C-26 hydroxylation [6], and PAG1 is closely related to BAS1 [7], suggesting that PAG1 might function to BAS1 in the inactivation of CS and BL
The results showed that the average content of CS was 0.340 ng/g in Chinese cotton research institution 24 (CCRI24) plants and 0.204 ng/g in pag1 plants (Table 1); the test of significant differences showed that the contents of CS were significantly lower in pag1 plants than in CCRI24 plants (Table 1)

Summary

Introduction

Brassinosteroids (BRs) play crucial roles in drought tolerance, but the underlying molecular mechanisms remain unclear in the important oilseed and fiber crop, cotton (Gossypium hirsutum L.). CYP734A1/ BAS1, a cytochrome P450 monooxygenase, catalyzes the C-26 hydroxylation of castasterone (CS) and brassinolide (BL), which are active BRs [5, 6]. PAG1 is the cotton homolog of CYP734A1/BAS1 and encodes a cytochrome. A study by Kagale showed that 24-epiBL (24-epibrassinolide) treatment could enhance drought tolerance in both Arabidopsis thaliana and B. napus seedlings [8]. Another study demonstrated that BRs could enhance tolerance to oxidative stress induced by polyethylene glycol (PEG) treatment through BRinduced NO production and NO-activated ABA biosynthesis in maize leaves [10]. In cucumber, elevated H2O2 levels due to enhanced NADPH oxidase activity are involved in BR-induced tolerance to stresses, such as photo-oxidative and cold stress and Cucumber mosaic virus infection [11]. The Arabidopsis BR-deficient mutant det was found to be more sensitive to salt stress than

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