Xiao Zhang, Daoming Liu, Dong Gao, Weining Zhao, Huaying Du, Zeyu Qiu, Jie Huang, Peizheng Wen, Yongsheng Wang, Qi Li, Wenhui Wang, Haosen Xu, Jun He, Yuqiang Liu, Jianmin Wan.

Int J Mol Sci.; 2022 May 25;23(11):5946.  doi: 10.3390/ijms23115946.

Abstract

Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant-insect interaction remains largely unclear. Here, we report that CKs act as a positive regulator in rice resistance against brown planthopper (BPH), a devastating insect pest of rice. We found that BPH feeding promotes CK biosynthesis and signaling in rice. Exogenous application of CKs significantly increased the rice resistance to BPH. Increasing endogenous CKs by knocking out cytokinin oxidase/dehydrogenase (OsCKXs) led to enhanced resistance to BPH. Moreover, the levels of the plant hormone jasmonic acid (JA) and the expression of JA-responsive genes were elevated by CK treatment and in OsCKXs knockout plants. Furthermore, JA-deficient mutant og1 was more susceptible to BPH, and CK-induced BPH resistance was suppressed in og1. These results indicate that CK-mediated BPH resistance is JA-dependent. Our findings provide the direct evidence for the novel role of CK in promoting insect resistance, and demonstrate that CK-induced insect resistance is JA-dependent. These results provide important guidance for effective pest management strategies in the future.

See: https://pubmed.ncbi.nlm.nih.gov/35682620/

Figure 3: Increasing endogenous CKs level significantly enhances rice resistance against BPH. (A) A diagram of the molecular lesion in the ckx1 mutants generated by CRISPR/cas9 genome-editing technology. The protospacer adjacent motifs (PAM) sequence and guide RNA targeting sites are indicated by overlined and blue color, respectively. (B) Contents of iP and iPR in rice sheaths of WT (Kitaake) and ckx1 seedlings. (C) Representative image of WT and ckx1 mutant seedlings before BPH infestation. Seedling mortality rate (D) and representative image (E) of WT and ckx1 mutant at day seven post infestation with BPH. Scale bars, 3 cm. Values are mean ± SD, n = 3. Different lower-case letters on the columns indicate significant differences at p < 0.05 determined by one-way ANOVA with Tukey’s test.