The arabidopsis Myotubularin2 negatively regulates autophagy

Autophagy is an evolutionarily-conserved bulk degradation pathway of eukaryotic cells. Central to autophagy is the assembly of autophagosome, which is initiated by a local pool of phosphatidylinositol 3-phosphate (PtdIns3P, PI3P) at the phagophore assembly site (PAS). Myotubularins (MTMs) are a family of lipid phosphatases that catalyzes PI3P turnover. Several mammalian MTMs reduce the level of PI3P to inhibit autophagosome initiation. MTMs in S.cerevisiae and C.elegans, however, have been reported to participate in autophagosome completion, thus positively regulate autophagy. Arabidopsis has two MTMs with confirmed biochemical activities, yet whether either plays a role in autophagy remains elusive. By RNA sequencing, we found that the expression of autophagy genes was down-regulated in the mtm2 mutant, as well as the transcription of substances secreted to the extracellular space. Most genes were upregulated in response to salt stress after 1 h of salt treatment.