Guo Lei, Qi Yetong, Mu Yang, Zhou Jing, Lu Wenhe, Tian Zhendong
College of Agronomy, Northeast Agricultural University, Harbin, 150030, China.
Key Laboratory of Horticultural Plant Biology (HZAU), Ministry of Education.
Hortic Res. 2022 Feb 11;9. doi: 10.1093/hr/uhac010.
Plant receptor-like kinases (RLKs) regulate many processes in plants. Many RLKs perform significant roles in plant immunity. Lectin receptor-like kinases (LecRLKs) are a large family of RLKs. However, the function of most of LecRLKs is poorly understood. In this study, we show that a potato LecRLK, StLecRK-IV.1, is involved in plant immunity against Phytophthora infestans. As a negative regulator of immunity, StLecRK-IV.1 is down-regulated by P. infestans and activated by abscisic acid (ABA). The transient expression of StLecRK-IV.1 in Nicotiana benthamiana enhanced P. infestans leaf colonization significantly. In contrast, the disease lesion size caused by P. infestans was reduced in Virus-induced gene silencing (VIGS) of StLecRK-IV.1 orthologue in N. benthamiana, NbLecRK-IV.1, as well as in potato plants with stable RNA interference of StLecRK-IV.1. Tetraspanin-8 (StTET8) was identified to be interacting with StLecRK-IV.1 using a membrane yeast-2-hybrid system, which was further verified by co-immunoprecipitation, a luciferase complementation assay, and a bimolecular fluorescence complementary (BiFC) test. StTET8 is a positive immune regulator that restrains P. infestans infection. The co-expression of StLecRK-IV.1 with StTET8 antagonized the positive roles of StTET8 against P. infestans. Moreover, the co-expression of StTET8 with StLecRK-IV.1 affected the stability of StTET8, which was confirmed by a Western blot assay and confocal assay. Taken together, our work firstly revealed that a potato L-type Lectin RLK, StLecRK-IV.1, negatively regulates plant immunity by targeting a positive regulator, StTET8, through affecting its stability.
植物类受体激酶（RLKs）调控植物中的许多过程。许多RLKs在植物免疫中发挥重要作用。凝集素类受体激酶（LecRLKs）是RLKs中的一个大家族。然而，大多数LecRLKs的功能仍知之甚少。在本研究中，我们表明马铃薯凝集素类受体激酶StLecRK-IV.1参与了植物对致病疫霉的免疫反应。作为免疫的负调控因子，StLecRK-IV.1在致病疫霉侵染下表达下调，并被脱落酸（ABA）激活。StLecRK-IV.1在本氏烟草中的瞬时表达显著增强了致病疫霉在叶片上的定殖。相反，在本氏烟草中对StLecRK-IV.1的同源基因NbLecRK-IV.1进行病毒诱导基因沉默（VIGS），以及在对StLecRK-IV.1进行稳定RNA干扰的马铃薯植株中, 由致病疫霉引起的病斑大小均减小。利用膜酵母双杂交系统鉴定出四跨膜蛋白8（StTET8）与StLecRK-IV.1相互作用，这一结果通过免疫共沉淀、荧光素酶互补试验和双分子荧光互补（BiFC）试验进一步得到验证。StTET8是一种抑制致病疫霉感染的正向免疫调节因子。StLecRK-IV.1与StTET8共表达拮抗了StTET8对致病疫霉的正向作用。此外, StTET8与StLecRK-IV.1共表达影响了StTET8的稳定性，这一结果通过蛋白质免疫印迹分析和共聚焦分析得到证实。综上所述，我们的工作首次揭示了马铃薯L型凝集素RLK StLecRK-IV.1通过靶向正向调节因子StTET8并影响其稳定性来负向调控植物免疫。
