Role of reactive oxygen species (ROS) signaling pathway in the wound-induced spore formation of Pyropia yezoensis

Asexual spore formation of Pyropia yezoensis significantly impacts yield. After mechanical sectioning of leafy thalli into fragments, somatic cells rapidly develop into a large number of wound-induced spores (WIS, a form of asexual spores). Recent studies on P. yezoensis have demonstrated a notable increase in reactive oxygen species (ROS) during this process; however, the regulatory mechanism underlying this ROS signaling remains largely unclear. This paper shows that in P. yezoensis, ROS signals play a crucial role in WIS formation. When treated with the ROS-producing enzyme NADPH oxidase inhibitor diphenyleneiodonium chloride, P. yezoensis thalli fragments strongly repressed WIS formation, accompanied by a significant decrease of ROS levels, malondialdehyde contents, and activities of NADPH oxidase and antioxidant enzymes. The expression levels of respiratory burst oxidase homolog genes, aquaporin protein genes, superoxide dismutase genes, glutathione S-transferase genes, and glutathioneperoxidase genes were also decreased, thus inhibiting WIS formation. As an upstream signal, ROS promote ion exchange and metabolism both inside and outside of cells within the first 12 h of wound stress. Following 12 h of wound stress, transcriptional activation of specific genes associated with cell cycle progression—which promotes cell division and dedifferentiation under normal conditions—was also blocked by diphenyleneiodonium chloride. In addition, the generated ROS signals also regulated the expression of mitogen-activated protein kinase family genes under wound stress. Overall, this study provides novel insights into the molecular mechanism underlying the ROS signaling regulation of WIS formation in P. yezoensis.