S-acylation of a geminivirus C4 protein is essential for regulating the CLAVATA pathway in symptom determination.

Geminiviruses, such as beet severe curly top virus (BSCTV), are a group of DNA viruses that cause severe plant diseases and agricultural losses. The C4 protein is a major symptom determinant in several geminiviruses; however, its regulatory mechanism and molecular function in plant cells remain unclear. Here, we show that BSCTV C4 is S-acylated in planta, and that this post-translational lipid modification is necessary for its membrane localization and functions, especially its regulation of shoot development of host plants. Furthermore, the S-acylated form of C4 interacts with CLAVATA 1 (CLV1), an important receptor kinase in meristem maintenance, and consequentially affects the expression of WUSCHEL, a major target of CLV1. The abnormal development of siliques in Arabidopsis thaliana infected with BSCTV is also dependent on the S-acylation of C4, implying a potential role of CLAVATA signaling in this process. Collectively, our results show that S-acylation is essential for BSCTV C4 function, including the regulation of the CLAVATA pathway, during geminivirus infection.

Two homologous protein S-acyltransferases, PAT13 and PAT14, cooperatively regulate leaf senescence in Arabidopsis.

Lipid modification on the cysteine residues of proteins, known as S-palmitoylation or S-acylation, regulates the subcellular localization and the function of proteins. S-acylation is catalysed by a group of protein acyltransferases (PATs) with a conserved Asp-His-His-Cys (DHHC) motif. The molecular function of S-acylation has been studied in details in yeast and mammalian cells, but its role in plant cells remains unclear. Here it is reported that the expression of two homologous protein acyltransferases- PAT13 and PAT14 -was moderately increased in the older leaves of Arabidopsis. The double mutant of PAT13 and PAT14 displayed a severely early leaf senescence phenotype. The phenotype was complemented by PAT13 or PAT14 overexpression in the double mutant, confirming the roles of PAT13 and PAT14 in this process. Furthermore, the levels of reactive oxygen species (ROS) and cell death were dramatically induced in the double mutant. To investigate the molecular functions of PAT13 and PAT14, their potential S-acylation substrates were predicted by bioinformatics methods. The subcellular localization and S-acylation of a candidate substrate NITRIC OXIDE ASSOCIATED 1 (NOA1), which also plays a role in leaf senescence control, were partially disrupted in the protoplasts of the double mutant. Impairment of S-acylation on NOA1 affected its subcellular localization and its function in leaf senescence regulation. Conclusively, protein S-acyltransferases PAT13 and PAT14 are involved in leaf senescence control- possibly via NOA1 S-acylation-, providing a new sight into the regulation mechanism of S-acylation in leaf senescence.