Dehydration rates impact physiological, biochemical and molecular responses in desert moss Bryum argenteum

Dehydration rates significantly impact the amount of damage and rate of recovery of desiccation-tolerant mosses and thus play a role in the ability of these plants to occupy desert ecosystems. The desiccation-tolerant moss Bryum argenteum Hedw. is a component of biological soil crusts in northwestern China and has been extensively studied, but the effects of dehydration rates on its physiological and molecular responses to desiccation and rehydration are still unclear. We evaluated the physiological, biochemical, and molecular responses of B. argenteum during and upon recovery from rapid dehydration, ambient air dehydration, and slow dehydration rates. Our results demonstrated that (1) photosynthesis decreased significantly in response to all dehydration rates and recovered to the control level following rehydration; however, recovery from slow dehydration was more rapid. Ultrastructural investigations revealed that chloroplasts did not degrade and remained intact during desiccation regardless of the dehydration rates. (2) The activities of antioxidant enzymes increased under all drying regimes. Superoxide dismutase (SOD) and catalase (CAT) were the main scavenging enzymes that responded during the dehydration and rehydration processes. The transcripts encoding these enzymes also increased in abundance during desiccation and rehydration. (3) The extent of the increase of the abundance of stress-related transcripts was correlated with the dehydration rates, and all the transcripts displayed decreased abundance throughout rehydration. The majority of the transcripts showed similar accumulation patterns under the rapid and air dehydration treatments; however, slow dehydration resulted in a greater increase in transcript abundance. Our work provides insights into how desiccation and rehydration play roles in the ability of B. argentum to endure harsh environments.