Pexophagy suppresses ROS-induced damage in leaf cells under high-intensity light

Although light is essential for photosynthesis, it has the potential to elevate intracellular levels of reactive oxygen species (ROS). Since high ROS levels are cytotoxic, plants must alleviate such damage. However, the cellular mechanism underlying ROS-induced leaf damage alleviation in peroxisomes was not fully explored. Here, we show that autophagy plays a pivotal role in the selective removal of ROS-generating peroxisomes, which protects plants from oxidative damage during photosynthesis. We present evidence that autophagy-deficient mutants show light intensity-dependent leaf damage and excess aggregation of ROS-accumulating peroxisomes. The peroxisome aggregates are specifically engulfed by pre-autophagosomal structures and vacuolar membranes in both leaf cells and isolated vacuoles, but they are not degraded in mutants. ATG18a-GFP and GFP-2×FYVE, which bind to phosphatidylinositol 3-phosphate, preferentially target the peroxisomal membranes and pre-autophagosomal structures near peroxisomes in ROS-accumulating cells under high-intensity light. Our findings provide deeper insights into the plant stress response caused by light irradiation

Rhizobial and Fungal Symbioses Show Different Requirements for Calmodulin Binding to Calcium Calmodulin–Dependent Protein Kinase in Lotus japonicus[W][OA]

Leguminous plants have mutualistic symbiotic relationships with rhizobial bacteria and arbuscular mycorrhizal fungi. These two distinct symbioses share calcium calmodulin–dependent protein kinase (CCaMK), a key regulator for accommodation of bacterial and fungal symbionts. This article demonstrates that the two symbioses are distinguished by differential regulation of CCaMK by calmodulin binding

Synergistic N2-fixation and salt stress mitigation in soybean through dual inoculation of ACC deaminase-producing Pseudomonas and Bradyrhizobium

Abstract We investigated the potential dual application of two Bradyrhizobium strains (B. diazoefficiens USDA110 and B. ottawaense SG09) and plant growth-promoting bacteria, PGPB (Pseudomonas spp.: OFT2 and OFT5), to improve nodulation and N2-fixation in soybean plants. The growth-promoting effects of dual inoculation were observed on plant growth, physiology, and nodulation of soybean under normal conditions compared with plants individually inoculated with either USDA110 or SG09. Both OFT2 and OFT5 promoted N2-fixation by 11% and 56%, respectively, when dual inoculation with USDA110 and by 76% and 81%, respectively, when dual inoculation with SG09. Salinity stress significantly reduces soybean growth, physiology, nutrient uptake, nodulation, and N2-fixation. However, these adverse effects were attenuated by the dual inoculation of PGPB and rhizobia depending on the combination of inoculants. In particular, dual inoculation of PGPB with SG09 was more effective in enhancing the salt tolerance of soybean by reducing salt-induced ethylene production and improving nutrient uptake. However, no such effect was observed with the combined inoculation of USDA110 and OFT5. An effective symbiotic association between SG09 and two Pseudomonas bacteria can be considered a beneficial approach to improving the symbiotic efficiency of nodulation and mitigating salinity stress in soybeans

Bradyrhizobium ottawaense efficiently reduces nitrous oxide through high nosZ gene expression

Abstract N2O is an important greenhouse gas influencing global warming, and agricultural land is the predominant (anthropogenic) source of N2O emissions. Here, we report the high N2O-reducing activity of Bradyrhizobium ottawaense, suggesting the potential for efficiently mitigating N2O emission from agricultural lands. Among the 15 B. ottawaense isolates examined, the N2O-reducing activities of most (13) strains were approximately five-fold higher than that of Bradyrhizobium diazoefficiens USDA110T under anaerobic conditions. This robust N2O-reducing activity of B. ottawaense was confirmed by N2O reductase (NosZ) protein levels and by mitigation of N2O emitted by nodule decomposition in laboratory system. While the NosZ of B. ottawaense and B. diazoefficiens showed high homology, nosZ gene expression in B. ottawaense was over 150-fold higher than that in B. diazoefficiens USDA110T, suggesting the high N2O-reducing activity of B. ottawaense is achieved by high nos expression. Furthermore, we examined the nos operon transcription start sites and found that, unlike B. diazoefficiens, B. ottawaense has two transcription start sites under N2O-respiring conditions, which may contribute to the high nosZ expression. Our study indicates the potential of B. ottawaense for effective N2O reduction and unique regulation of nos gene expression towards the high performance of N2O mitigation in the soil