4-Coumarate-CoA Ligase-Like Gene OsAAE3 Negatively Mediates the Rice Blast Resistance, Floret Development and Lignin Biosynthesis

Abstract

Although adenosine monophosphate (AMP) binding domain is widely distributed in multiple plant species, detailed molecular functions of AMP binding proteins (AMPBPs) in plant development and plant-pathogen interaction remain unclear. In the present study, we identified an AMPBP <i>OsAAE3</i> from a previous analysis of early responsive genes in rice during <i>Magnaporthe oryzae</i> infection. <i>OsAAE3</i> is a homolog of Arabidopsis <i>AAE3</i> in rice, which encodes a 4-coumarate-Co-A ligase (4CL) like protein. A phylogenetic analysis showed that <i>OsAAE3</i> was most likely <i>4CL-like 10</i> in an independent group. <i>OsAAE3</i> was localized to cytoplasm, and it could be expressed in various tissues. Histochemical staining of transgenic plants carrying <i>OsAAE3</i> promoter-driven GUS (β-glucuronidase) reporter gene suggested that <i>OsAAE3</i> was expressed in all tissues of rice. Furthermore, <i>OsAAE3-OX</i> plants showed increased susceptibility to <i>M. Oryzae</i>, and this finding was attributable to decreased expression of pathogen-related 1a (<i>PR1</i>) and low level of peroxidase (POD) activity. Moreover, <i>OsAAE3</i> over-expression resulted in increased content of H₂O₂, leading to programmed cell-death induced by reactive oxygen species (ROS). In addition, <i>OsAAE3</i> over-expression repressed the floret development, exhibiting dramatically twisted glume and decreased fertility rate of anther. Meanwhile, the expressions of lignin biosynthesis genes were significantly decreased in <i>OsAAE3-OX</i> plants, thereby leading to reduced lignin content. Taken together, <i>OsAAE3</i> functioned as a negative regulator in rice blast resistance, floret development, and lignin biosynthesis. Our findings further expanded the knowledge in functions of AMBPs in plant floret development and the regulation of rice-fungus interaction.