Desiccation Tolerant Pv11 Cells Maintain Organelle Organization During Drying and Rehydration

Abstract

Polypedilum vanderplanki is an anhydrobiotic midge, whose larva are capable of surviving virtually complete desiccation and enter an ametabolic state (i.e. anhydrobiosis). Previous studies have shown that various anhydrobiosis-related intrinsically disordered (ARID) and chaperone proteins, expanded antioxidant systems, and accumulation of the non-reducing disaccharide trehalose are molecular strategies largely responsible for anhydrobiosis in P. vanderplanki. Nevertheless, how membrane-bound and membraneless organelles behave during desiccation remains uncharacterized. Here we characterize the morphological responses of mitochondria and nucleoli during desiccation and rehydration in desiccation-tolerant Pv11 cells. Preincubating Pv11 cells, a cell line established from P. vanderplanki, with a 600 mM trehalose solution supplemented with just 10% of culture media for 48 h hours is required for the cells to enter and exit anhydrobiosis but also causes severe autophagy, as judged by the formation of large autophagosomes. In the absence of trehalose preincubation prior to desiccation, rehydration caused extensive swelling of cells (“ballooning”) and the concurrent loss of intracellular integrity. In trehalose preconditioned Pv11 cells, the mitochondria lose their membrane potential upon desiccation, but the organelle maintains its membrane integrity. Upon rehydration of trehalose-preconditioned Pv11 cells, mitochondria regain their membrane potential within 30 min. Strikingly, preincubation with trehalose also protected the nucleolus, a membraneless organelle. In cells not preincubated with trehalose a visible nucleolus was not maintained, although the nuclear envelope appeared to be intact. These data demonstrate that trehalose preincubation causes significant intracellular changes in addition to the accumulation of trehalose, that the mitochondria membrane potential in cells of anhydrobiotic animals are rapidly reestablished upon rehydration, and that membraneless organelles are being preserved in the desiccated state.