One explanation is that Rab32 may function in these different processes in a similar way. Alternatively, Rab32 could affect the lysosome and lysosome-related processes, subsequently influencing lipid storage. These results suggest that in autophagy mutants, more lipids may be mobilized from lipid droplets to compensate for the shortage of energy. It is conceivable that by affecting autophagy, Rab32 likely regulates lipid storage through lipolysis. The genetic interactions between Rab32/ltd and lipolysisrelated genes, bmm and plin2, further support this hypothesis. This study has highlighted the potential functions of Rabs in regulating lipid metabolism. Further studies will elucidate the intermingled relationship between autophagy and lipid Shikonofuran-A metabolism during development. MAP kinases phosphorylate their substrates on conserved Ser/ Thr-Pro phosphoacceptor sites. However, targeting of a MAP kinase to a specific substrate does not only depend on the phosphoacceptor site, but is also mediated by physical interaction between the kinase and MAP kinase docking domains present on substrate protein. We show that a loss-of-function mks1 insertion allele is a much stronger suppressor of mpk4 than MKS1-RNAi. In addition, we found that this mks1 mutant exhibits decreased basal resistance to biotrophic pathogens, an effect not seen in plants with reduced accumulation of MKS1 mRNA via RNAi. These observations are important because they demonstrate that MKS1 plays a role in maintaining basal resistance at levels similar to that found for other resistance signaling proteins like EDS1 and PAD4. That MKS1 plays important roles in plant resistance responses is further supported by the recent finding that the Procyanidin-B2 snc4-1D mutant, which exhibits increased resistance responses, is partially suppressed by mks1. MKS1 interacts with both MPK4 and WRKY33. Using directed yeast two-hybrid screens with different MKS1 deletion forms, we found that the N-terminal domain, which contains a putative kinase docking domain, interacts with MPK4, whereas WRKY33 was found to interact with a plant-specific VQ motifcontaining domain. MKS1 is a member of a small protein family sharing this conserved VQ motif of unknown function, but other than this region their primary structures are highly diverse.