Abstract
The phospholipids metabolism has been known to play an important role in both animals and plants. In plants, phospholipase D (PLD) has been suggested to be involved in many plant cellular processes, such as signaling for stress and hormone responses. Plant PLDs are a family of heterologous enzymes and 12 PLD genes in arabidopsis and 17 ones in rice were reported. They can be classified into several types based on their gene architectures, sequence similarities, domain structures, and biochemical properties. To examine the physiological function of PLD in rice, we made knockdown plants for each PLD isoform by introducing gene-specific RNAi constructs. One of them, OsPLDβ1-knockdown plants showed the accumulation of reactive oxygen species in the absence of pathogen infection. RT-PCR and DNA microarray analyses revealed that the knockdown of OsPLDβ1 resulted in the up-/down-regulation of more than 1,400 genes, including the induction of defense-related genes such as PR protein genes and WRKY/ERF family transcription factor genes. HR-like cell death and phytoalexin production were also observed at a later phase of growth in the OsPLDβ1-knockdown plants. These results indicated that the OsPLDβ1-knockdown plants spontaneously activate the defense responses in the absence of pathogen infection.
