Brassinosteroids mediate susceptibility to brown planthopper by integrating with the salicylic acid and jasmonic acid pathways in rice.

Gen Pan,Tingting Xu,Linglong Liu,Jianmin Wan,Yuqiang Liu,Jie Huang,Xiao Zhang,Ling Jiang,Zhiguang Sun,Chunming Wang,Zeyu Qiu,Xianian Cheng,Daoming Liu,Jun He,Linshan Ji

doi:10.1093/jxb/ery223

Abstract

Improved knowledge of the interactions between plants and insects will facilitate better insect control in crops. Brassinosteroids (BRs) play a vital role in plant growth, developmental processes, and responses to pathogen infection, but the role of BRs in interactions between plants and insects remain largely unknown. In this study, we characterized a negative role of BRs in rice defense against brown planthopper (BPH, Nilaparvata lugens) and examined its underlying mechanisms. We found that BPH infestation suppressed the BR pathway while successively activating the salicylic acid (SA) and jasmonic acid (JA) pathways. In addition, BR-overproducing mutants and plants treated with 24-epibrassinolide (BL) showed increased susceptibility to BPH, whereas BR-deficient mutants were more resistant than the wild-type. BRs down-regulated the expression of genes related to the SA pathway and reduced SA content while genes related to the JA pathway were up-regulated and JA content increased after BPH infestation. Furthermore, BR-mediated suppression of the SA pathway was impaired both in JA-deficient and JA-insensitive mutants. Our results demonstrate that BRs promote the susceptibility of rice plants to BPH by modulating the SA and JA pathways.

Highlights

Rice (Oryza sativa L.) is one of the most important staple foods, feeding over half of the world population
BRs down-regulated the expression of genes related to the salicylic acid (SA) pathway and reduced SA content while genes related to the jasmonic acid (JA) pathway were up-regulated and JA content increased after brown planthopper (BPH) infestation
BPH infestation inhibits the BR pathway and activates the SA and JA pathways To determine the role of BRs in rice defense against BPH, transcript levels of BR pathway-related genes were determined following BPH infestation. Quantitative RT-PCR (qRT-PCR) showed that expression levels of the BR receptor BR INSENSITIVE 1 (BRI1) and the BR signaling component BRASSINAZOLE RESISTANT 1 (BZR1) were decreased, especially at 24 h post-BPH infestation (Fig. 1A)

Summary

Introduction

Rice (Oryza sativa L.) is one of the most important staple foods, feeding over half of the world population. At least eight BPH-resistance genes have been cloned, knowledge of the underlying molecular mechanisms of plant–BPH. Bph, Bph, Bph, and Bph as well as the aphid-resistance gene Mi1.2 have been categorized as genes that produce the coiled-coil nucleotide-binding site and leucine-rich repeat motif proteins (CC-NB-LRR) that are known to mediate resistance through direct or indirect recognition of pathogen effectors in rice (Rossi et al, 1998; Du et al, 2009;Tamura et al, 2014; Ji et al, 2016; Liu and Wang, 2016; Zhao et al, 2016)

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