The auxiliary ESCRT complexes provide robustness to cold in poikilothermic organisms

The ESCRT pathway, comprising the in sequence acting ESCRT-0, -I, -II, -III and Vps4 complexes, conducts the abscission of membranes away from the cytosol. Whereas the components of the central ESCRT-III core complex have been thoroughly investigated, the function of the components of the associated two auxiliary ESCRT sub-complexes are not well-understood in metazoans, especially at the organismal level. We here present the developmental analysis of the Drosophila orthologs of the auxiliary ESCRTs Chmp5 and Ist1, DChmp5 and DIst1, which belong to the two auxiliary sub-complexes. While each single null mutant displayed mild defects in development, the Dist1 Dchmp5 double mutant displayed a severe defect, indicating that the two genes act synergistically, but in separate pathways. Moreover, the presented results indicate that the auxiliary ESCRTs provide robustness against cold during development of diverse poikilothermic organisms, probably by preventing the accumulation of the ESCRT-III core component Shrub on the endosomal membrane.