Regulation of xylanase elicitor-induced expression of defense-related genes involved in phytoalexin biosynthesis by a cation channel OsTPC1 in suspension-cultured rice cells

Signal molecules derived from pathogens/microbes or plants (pathogen/microbe/damage-associated molecular patterns; PAMPs/MAMPs/DAMPs), elicitors, trigger changes in cytosolic free Ca2+ concentrations ([Ca2+](cyt)) to activate plant immune responses. A rice two-pore channel 1 (OsTPC1) has been suggested to be involved in fungal xylanase elicitor (TvX)-induced defense responses including [Ca2+](cyt) increase, phytoalexin production and hypersensitive cell death in suspension-cultured rice cells. However, little is known on the molecular links between [Ca2+](cyt) rise and elicitor-induced gene expression. To gain insights on the possible roles of OsTPC1 in TvX-induced gene expression, we performed DNA microarray analysis using a rice 44K oligo-microarray system, and revealed that TvX induce expression of thousands of genes including WRKY-type transcription factors, a serine hydrolase involved in hypersensitive cell death, and diterpene cyclases required for phytoalexin biosynthesis, which are suppressed in the Ostpc1 knockout mutant. TvX-induced expression of genes involved in the methylerythritol phosphate (MEP) pathway, which is located upstream of the phytoalexin biosynthesis pathway, was also suppressed in Ostpc1 cells. Possible involvement of OsTPC1 in the regulation of gene expression and metabolism in cultured-rice cells is discussed.