Functional Analysis of Brassinosteroids in Salt Stress Responses in Rice

doi:10.11983/CBB19013

Abstract

Abstract: Brassinosteroids (BRs) are a class of steroid phytohormones that play diverse roles in plant growth and development and stress responses. Rapid progresses have been made in how BRs regulate plant growth and development in recent years. However, the roles of BRs in stress response in Oryza sativa remain unclear. Here, we investigated the relation between salinity stress and BR synthesis in rice. Both salt stress and abscisic acid, the well-known stress hormone, strongly inhibited the expression of two BR-synthetic genes, D2 and D11. In addition, both d2-2, the BR synthetic mutant, and d61-1, the BR receptor mutant, showed impaired tolerance to salt stress. Moreover, by using transgenic plants overexpressing OsBZR1, the key BR signaling transcriptional factor, we found that BRs strongly induced dephosphorylation of OsBZR1, but high concentrations of salt suppressed OsBZR1 protein accumulation as well as its dephosphorylation. Furthermore, transcriptome analyses revealed that 38.4% of BR-regulated genes were also regulated by high concentrations of salt, and importantly, 91.5% of the co-regulated genes are consistently up- or downregulated by both BR and salt. Gene Ontology analyses revealed that these overlapping genes were highly enriched in the biological process “response to stimulus”. Taken together, our results suggest that BRs contribute to salt stress tolerance, and salt stress suppresses BR synthesis to restrict rice growth.

Key words: brassinosteroid, rice, salt stress, abscisic acid, OsBZR1

Lulu Li,Wenchao Yin,Mei Niu,Wenjing Meng,Xiaoxing Zhang,Hongning Tong. Functional Analysis of Brassinosteroids in Salt Stress Responses in Rice[J]. Chinese Bulletin of Botany, 2019, 54(2): 185-193.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB19013

https://www.chinbullbotany.com/EN/Y2019/V54/I2/185

Figures/Tables 6

Figure 1 Time-course expression of BR synthetic genes in rice following salt or ABA treatment(A) D2 expression after NaCl treatment; (B) D11 expression after NaCl treatment; (C) D2 expression after ABA treatment; (D) D11 expression after ABA treatment. * P<0.05; *** P<0.001

Figure 2 Survival rate of rice BR defective mutants and the wild type under salt stress(A) Growth status of d2-2 mutant and the wild type after salt treatment; (B) Statistic data of the survival rate of d2-2 and the wild type after salt treatment; (C) Growth status of d61-1 mutant and the wild type after salt treatment; (D) Statistic data of the survival rate of d61-1 and the wild type after salt treatment. ** P<0.01

Figure 3 Effects of BR and salt stress on OsBZR1 proteins in rice(A) Effect of BR treatment on OsBZR1 proteins; (B) Effect of salt treatment on OsBZR1 proteins

Figure 4 Co-regulation analyses of BR-, ABA- and NaCl-regulated genes of rice(A) Co-regulated gene numbers between BR-, ABA- and NaCl-regulated different expression genes (DEGs); (B) Co-regulation analyses among BR-upregulated (BR-UP), BR-downregulated (BR-DN), NaCl-upregulated (NaCl-UP) and NaCl-downregulated (NaCl-DN) genes. Distribution of the gene numbers was indicated.

Figure 5 Gene Ontology analyses of the 189 BR-NaCl co-regulated genes of rice(A) GO analyses in term of the biological process; (B) GO analyses in terms of biological process, cellular component, and molecular function

Figure 6 Proposed model for BR function in salt stress res- ponses in rice

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