Synaptotagmin 4 and 5 additively contribute to Arabidopsis immunity to DC3000.

Soluble -ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are essential for vesicle trafficking in plants. Vesicle-associated membrane protein 721 and 722 (VAMP721/722) are secretory vesicle-localized R-SNAREs, which are involved in a variety of biological processes in plants. Compared to VAMP721/722, a VAMP721/722-interacting plasma membrane (PM)-localized Qa-SNARE is engaged in a rather specific physiological process. This indicates that an in vivo regulator controls an interaction between a Qa-SNARE and VAMP721/722 for a specific cellular activity. We previously reported that synaptotagmin 5 (SYT5) modulates the interaction between SYP132 PM Qa-SNARE and VAMP721/722 for Arabidopsis resistance to DC3000. In this study, we show that defense against DC3000 is compromised in SYT4-lacking plants, which belongs to the same subclade as SYT5. Further elevation of bacterial growth in plants compared to either or single mutant suggests that SYT4 and SYT5 play additive roles in Arabidopsis immunity to DC3000.