Role of ROS signaling pathway in the wound-induced spore formation of Pyropia yezoensis

Asexual spore formation of Pyropia yezoensis has significant impacts on its yield. After the leafy thalli were mechanically sectioned into fragments, the somatic cells rapidly developed into large number of asexual spores (wound-induced spores, WIS). Recent studies have demonstrated a notable increase in reactive oxygen species (ROS) during this process in P. yezoensis, however, the regulatory mechanism of ROS signaling remains largely unclear. Here, we report that the ROS signals plays a crucial role in WIS formation of P. yezoensis. When treated with the inhibitor of ROS-producing enzyme NADPH oxidase, diphenyleneiodonium chloride (DPI), Pyropia thalli fragments exhibited strong repression in WIS formation, accompanying with significantly decreased ROS level, malondialdehyde content and the activities of NADPH oxidase and antioxidant enzymes. Furthermore, the expression of PyRBOHs, PyAQPs genes and antioxidant enzyme genes PySODs, PyGPXs, and PyGSTs were also decreased, leading to the inhibition of WIS formation. Moreover, ROS, as an upstream signal, promotes ion exchange and metabolism both inside and outside the cells within the 12 hours under wound stress. After 12 hours of wounding, transcriptional activation of specific genes associated with cell cycle progression, which promoted cell division and dedifferentiation in normal condition, were also blocked by DPI. In addition, the generated ROS signals also regulated the expression of MAPK family genes under wound stress. Overall, our study provides novel insights into the molecular mechanism of ROS signaling regulates WIS formation in P. yezoensis.