Comprehensive Phosphoproteomic Analysis of Nostoc flagelliforme in Response to Dehydration Provides Insights into Plant ROS Signaling Transduction

Terrestrial cyanobacteria,
originated from aquatic cyanobacteria,
exhibit a unique mechanism for drought adaptation during long-term
evolution. To elucidate this diverse adaptive mechanism exhibited
by terrestrial cyanobacteria from the post-translation modification
aspect, we performed a global phosphoproteome analysis on the abundance
of phosphoproteins in response to dehydration using Nostoc flagelliforme, a kind of terrestrial cyanobacteria
having strong ecological adaptability to xeric environments. A total
of 329 phosphopeptides from 271 phosphoproteins with 1168 phosphorylation
sites were identified. Among these, 76 differentially expressed phosphorylated
proteins (DEPPs) were identified for each dehydration treatment (30,
75, and 100% water loss), compared to control. The identified DEPPs
were functionally categorized to be mainly involved in a two-component
signaling pathway, photosynthesis, energy and carbohydrate metabolism,
and an antioxidant system. We concluded that protein phosphorylation
modifications related to the reactive oxygen species (ROS) signaling
pathway might play an important role in coordinating enzyme activity
involved in the antioxidant system in N. flagelliforme to adapt to dehydration stress. This study provides deep insights
into the extensive modification of phosphorylation in terrestrial
cyanobacteria using a phosphoproteomic approach, which may help to
better understand the role of protein phosphorylation in key cellular
mechanisms in terrestrial cyanobacteria in response to dehydration.