The Arabidopsis thaliana PATL1 functions downstream of CaM3 to mediate vesicle trafficking under the heat shock pathway.

Although vesicle trafficking is highly responsive to various environmental triggers, its role in thermotolerance remains unclear. Arabidopsis thaliana Patellin 1 (PATL1) plays a crucial role in vesicle trafficking. To elucidate the role of PATL1-mediated vesicle trafficking in thermotolerance, we investigated PATL1 function under heat shock (HS) conditions and found PATL1 inhibited vesicle trafficking, leading to a decreased accumulation of HS proteins (HSPs), indicating a negative correlation with thermotolerance. Previously, we reported that the calmodulin (CaM) isoform, CaM3, is involved in heat tolerance. In the present study, we found that CaM3 binds to and inhibits PATL1, thereby promoting HSP accumulation. This interaction reduces the binding of PATL1 to phosphatidylinositol diphosphate, thereby facilitating vesicle transport. In summary, our study elucidates a non-canonical CaM3 signaling pathway in which PATL1 acts as a downstream factor to enhance HSP accumulation through vesicle trafficking.