Institute for Plant Genomics & Biotechnology, Texas A&M University, College Station, TX 77843, USA; Department of Plant Pathology & Microbiology, Texas A&M University, College Station, TX 77843, USA.
Institute for Plant Genomics & Biotechnology, Texas A&M University, College Station, TX 77843, USA; Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843, USA; College of Plant Protection, China Agricultural University, Beijing 100193, P.R. China.
Curr Biol. 2019 Nov 18;29(22):3778-3790.e8. doi: 10.1016/j.cub.2019.09.018. Epub 2019 Oct 31.
Cell death is a vital and ubiquitous process that is tightly controlled in all organisms. However, the mechanisms underlying precise cell death control remain fragmented. As an important shared module in plant growth, development, and immunity, Arabidopsis thaliana BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1) and somatic embryogenesis receptor kinase 4 (SERK4) redundantly and negatively regulate plant cell death. By deploying an RNAi-based genetic screen for bak1/serk4 cell death suppressors, we revealed that cyclic nucleotide-gated channel 20 (CNGC20) functions as a hyperpolarization-activated Ca-permeable channel specifically regulating bak1/serk4 cell death. BAK1 directly interacts with and phosphorylates CNGC20 at specific sites in the C-terminal cytosolic domain, which in turn regulates CNGC20 stability. CNGC19, the closest homolog of CNGC20 with a low abundance compared with CNGC20, makes a quantitative genetic contribution to bak1/serk4 cell death only in the absence of CNGC20, supporting the biochemical data showing homo- and heteromeric assembly of the CNGC20 and CNGC19 channel complexes. Transcripts of CNGC20 and CNGC19 are elevated in bak1/serk4 compared with wild-type plants, further substantiating a critical role of homeostasis of CNGC20 and CNGC19 in cell death control. Our studies not only uncover a unique regulation of ion channel stability by cell-surface-resident receptor kinase-mediated phosphorylation but also provide evidence for fine-tuning Ca channel functions in maintaining cellular homeostasis by the formation of homo- and heterotetrameric complexes.
细胞死亡是一种重要的、普遍存在的过程，在所有生物中都受到严格的控制。然而，精确控制细胞死亡的机制仍然很零散。作为植物生长、发育和免疫的一个重要共享模块，拟南芥 BRASSINOSTEROID INSENSITIVE 1 相关受体激酶 1（BAK1）和体细胞胚胎发生受体激酶 4（SERK4）冗余且负调控植物细胞死亡。通过利用基于 RNAi 的遗传筛选来寻找 bak1/serk4 细胞死亡抑制子，我们揭示了环核苷酸门控通道 20（CNGC20）作为一种超极化激活的钙通透通道，特异性调节 bak1/serk4 细胞死亡。BAK1 直接与 CNGC20 相互作用，并在 C 端胞质域的特定位点上磷酸化 CNGC20，从而调节 CNGC20 的稳定性。CNGC19 是 CNGC20 的最接近同源物，与 CNGC20 相比，其丰度较低，仅在没有 CNGC20 的情况下，对 bak1/serk4 细胞死亡有定量遗传贡献，这支持了生化数据表明 CNGC20 和 CNGC19 通道复合物的同型和异型组装。与野生型植物相比，CNGC20 和 CNGC19 的转录物在 bak1/serk4 中升高，进一步证实了 CNGC20 和 CNGC19 离子通道稳定性的重要作用在细胞死亡控制中。我们的研究不仅揭示了细胞表面驻留受体激酶介导的磷酸化对离子通道稳定性的独特调节作用，而且还为通过形成同型和异型四聚体复合物来精细调节 Ca 通道功能以维持细胞内稳态提供了证据。
