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Lesion mimic mutants (LMMs) have been widely used in experiments in recent years for studying plant physiological mechanisms underlying programmed cell death (PCD) and defense responses. Here, we identified a lesion mimic mutant, lm212-1, which cloned the causal gene by a map-based cloning strategy, and verified this by complementation. The causal gene, OsPHD1, encodes a UDP-glucose epimerase (UGE), and the OsPHD1 was located in the chloroplast. OsPHD1 was constitutively expressed in all organs, with higher expression in leaves and other green tissues. lm212-1 exhibited decreased chlorophyll content, and the chloroplast structure was destroyed. Histochemistry results indicated that H2O2 is highly accumulated and cell death is occurred around the lesions in lm212-1. Compared to the wild type, expression levels of defense-related genes were up-regulated, and resistance to bacterial pathogens Xanthomonas oryzae pv. oryzae (Xoo) was enhanced, indicating that the defense response was activated in lm212-1, ROS production was induced by flg22, and chitin treatment also showed the same result. Jasmonic acid (JA) and methyl jasmonate (MeJA) increased, and the JA signaling pathways appeared to be disordered in lm212-1. Additionally, the overexpression lines showed the same phenotype as the wild type. Overall, our findings demonstrate that OsPHD1 is involved in the regulation of PCD and defense response in rice. [ABSTRACT FROM AUTHOR]

Summary: Male reproductive development involves a complex series of biological events and precise transcriptional regulation is essential for this biological process in flowering plants. Several transcriptional factors have been reported to regulate tapetum and pollen development, however the transcriptional mechanism underlying Ubisch bodies and pollen wall formation remains less understood. Here, we characterized and isolated a male sterility mutant of TDR INTERACTING PROTEIN 3 (TIP3) in rice. The tip3 mutant displayed smaller and pale yellow anthers without mature pollen grains, abnormal Ubisch body morphology, no pollen wall formation, as well as delayed tapetum degeneration. Map‐based cloning demonstrated that TIP3 encodes a conserved PHD‐finger protein and further study confirmed that TIP3 functioned as a transcription factor with transcriptional activation activity. TIP3 is preferentially expressed in the tapetum and microspores during anther development. Moreover, TIP3 can physically interact with TDR, which is a key component of the transcriptional cascade in regulating tapetum development and pollen wall formation. Furthermore, disruption of TIP3 changed the expression of several genes involved in tapetum development and degradation, biosynthesis and transport of lipid monomers of sporopollenin in tip3 mutant. Taken together, our results revealed an unprecedented role for TIP3 in regulating Ubisch bodies and pollen exine formation, and presents a potential tool to manipulate male fertility for hybrid rice breeding. Significance Statement: TIP3, a PHD‐finger protein, functions as a transcriptional activator and physically interacts with TDR participating in tapetum programmed cell death, Ubisch body morphogenesis and pollen wall formation. Our results provide an insight into the molecular mechanism underlying tapetal programmed cell death (PCD) and pollen wall formation in rice. [ABSTRACT FROM AUTHOR]