Lesion mimic mutants constitute a valuable genetic resource for unraveling the signaling pathways and molecular mechanisms governing the programmed cell death and defense responses of plants. Here, we identified a lesion mimic mutant spl-D from T-DNA insertion rice lines. The mutant exhibited higher accumulation of H2O2, spontaneous cell death, decreased chlorophyll content, up-regulation of defense-related genes, as well as enhanced disease resistance. The causative gene OsGRDP1 encodes a cytosol and membrane-associated glycine-rich domain protein. OsGRDP1 was expressed constitutively in all of the organs of the wild-type plants, but it was upregulated throughout plant development in the spl-D mutant. Both the overexpression (OE) and knockdown (RNAi) of OsGRDP1 resulted in the lesion mimic phenotype. Moreover, the intact protein level of OsGRDP1 was reduced in the spotted leaves from both OE and RNAi plants, suggesting that the disruption of intact OsGRDP1 is responsible for lesion formation. OsGRDP1 interacted with an aspartic proteinase OsAP25. In the spl-D and OE plants, proteinase activity was elevated, and lesion formation was partially suppressed by the aspartic proteinase inhibitor. Taken together, our results indicate that OsGRDP1 is a critical feedback regulator, thus contributing to the elucidation of the mechanism underlying cell death and disease resistance.
Summary Lesion mimic mutants are used to elucidate mechanisms controlling plant responses to pathogen attacks and environmental stresses. Although dozens of genes had been functionally demonstrated to be involved in lesion mimic phenotype in several plant species, the molecular mechanisms underlying the hypersensitive response are largely unknown. Here, a rice (Oryza sativa) lesion mimic mutant natural blight leaf 3 (nbl3) was identified from T‐DNA insertion lines. The causative gene, OsNBL3, encodes a mitochondrion‐localized pentatricopeptide repeat (PPR) protein. The nbl3 mutant exhibited spontaneous cell death response and H2O2 accumulation, and displayed enhanced resistance to the fungal and bacterial pathogens Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae. This resistance was consistent with the up‐regulation of several defence‐related genes; thus, defence responses were induced in nbl3. RNA interference lines of OsNBL3 exhibited enhanced disease resistance similar to that of nbl3, while the disease resistance in overexpression lines did not differ from that of the wild type. In addition, nbl3 displayed improved tolerance to salt, accompanied by up‐regulation of several salt‐associated marker genes. OsNBL3 was found to mainly participate in the splicing of mitochondrial gene nad5 intron 4. Disruption of OsNBL3 leads to the reduction in complex I activity, the elevation of alternative respiratory pathways and the destruction of mitochondrial morphology. Overall, the results demonstrated that the PPR protein‐coding gene OsNBL3 is essential for mitochondrial development and functions, and its disruption causes the lesion mimic phenotype and enhances disease resistance and tolerance to salt in rice.
In animals, malectin is well known to play an essential role in endoplasmic reticulum quality control (ERQC) by interacting with ribophorin I, one unit of the oligosaccharyltransferase (OST) complex. However, the functions of malectin in plants remain largely unknown. Here, we demonstrate the rice OsMLD1 is an ER- and Golgi-associated malectin protein and physically interacts with rice homolog of ribophorin I (OsRpn1), and its disruption leads to spontaneous lesion mimic lesions, enhanced disease resistance, and prolonged ER stress. In addition, there are many more N-glycosites and N-glycoproteins identified from the mld1 mutant than wildtype. Furthermore, OsSERK1 and OsSERK2, which have more N-glycosites in mld1, were demonstrated to interact with OsMLD1. OsMLD1 can suppress OsSERK1- or OsSERK2-induced cell death. Thus, OsMLD1 may play a similar role to its mammalian homologs in glycoprotein quality control, thereby regulating cell death and immunity of rice, which uncovers the function of malectin in plants.
Background Plant senescence is a complicated process involving multiple regulations, such as temperature, light, reactive oxygen species (ROS), endogenous hormone levels, and diseases. Although many such genes have been characterized to understand the process of leaf senescence, there still remain many unknowns, and many more genes need to be characterized. Results We identified a rice mutant nbl1 with a premature leaf senescence phenotype. The causative gene, OsNBL1, encodes a small protein with 94 amino acids, which is conserved in monocot, as well as dicot plants. Disruption of OsNBL1 resulted in accelerated dark-induced leaf senescence, accompanied by a reduction in chlorophyll content and up-regulation of several senescence-associated genes. Notably, the nbl1 mutant was more susceptible to rice blast and bacterial blight but more tolerant to sodium chloride. Several salt-induced genes, including HAK1, HAK5, and three SNAC genes, were also up-regulated in the nbl1 mutant. Additionally, the nbl1 mutant was more sensitive to salicylic acid. Plants overexpressing OsNBL1 showed delayed dark-induced senescence, consistent with a higher chlorophyll content compared to wild-type plants. However, the overexpression plants were indistinguishable from the wild-types for resistance to the rice blast disease. OsNBL1 is a multi-organelle localized protein and interacts with OsClpP6, which is associated with senescence. Conclusions We described a novel leaf senescence mutant nbl1 in rice. It is showed that OsNBL1, a multi-organelle localized protein which interacts with a plastidic caseinolytic protease OsClpP6, is essential for controlling leaf senescence, disease resistance, and salt tolerance.
Lesion mimic mutants are used to elucidate mechanisms controlling plant responses to pathogen attacks and environmental stresses. Here, a new rice (Oryza sativa) lesion mimic mutant, natural blight leaf 3 (nbl3 ), was identified from T-DNA insertion lines. The causative gene, OsNBL3, encodes a mitochondria-localized pentatricopeptide repeat (PPR) protein. The nbl3 mutant exhibited spontaneous cell death and H 2 O 2 accumulation as evidenced by Trypan blue, 3,3'-diaminobenzidine and tetranitroblue tetrazolium chloride analyses. Additionally, nbl3 displayed enhanced resistance to the fungal and bacterial pathogens Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae. This resistance was consistent with the upregulation of several defence-related genes; thus defence responses were induced in nbl3. RNA interference lines of OsNBL3 exhibited enhanced disease resistance similar to that of nbl3, while the disease resistance of overexpression lines did not differ from that of the wild type. In addition, nbl3 displayed improved tolerance to salt treatment, accompanied by upregulation of several saltassociated marker genes. Disruption of OsNBL3 leads to destruction of mitochondria and elevated use of alternative respiratory pathways. OsNBL3 was found to mainly participate in the splicing of mitochondrial gene nad5 intron 4. Overall, the results demonstrated that a PPR protein was involved in disease resistance and salt tolerance in rice.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.