Pollardhusted0745

Ribulose-1,5-bisphosphate carboxylase/oxygenase, the key enzyme of photosynthetic carbon fixation, is able to accept both O2 and CO2 as substrates. When it fixes O2, it produces 2-phosphoglycolate, which is detoxified by photorespiration and recycled to the Calvin-Benson-Bassham cycle. To complete photorespiration, metabolite transport across three organelles, chloroplasts, peroxisomes, and mitochondria, is necessary through transmembrane transporters. In rice (Oryza sativa) little is known about photorespiratory transmembrane transporters. Here, we identified the rice plastidic glycolate/glycerate translocator 1 (OsPLGG1), a homolog of Arabidopsis PLGG1. PRT062070 solubility dmso OsPLGG1 mutant lines, osplgg1-1, osplgg1-2, and osplgg1-3, showed a growth retardation phenotype, such as pale green leaf, reduced tiller number, and reduced seed grain weight as well as reduced photosynthetic carbon reduction rate due to low activities of photosystem I and II. The plant growth retardation in osplgg1 mutants was rescued under high CO2 condition. Subcellular localization of OsPLGG1-GFP fusion protein, along with its predicted N-terminal transmembrane domain, confirmed that OsPLGG1 is a chloroplast transmembrane protein. Metabolite analysis indicated significant accumulation of photorespiratory metabolites, especially glycolate and glycerate, which have been shown to be transported by the Arabidopsis PLGG1, and changes for a number of metabolites which are not intermediates of photorespiration in the mutants. These results suggest that OsPLGG1 is the functional plastidic glycolate/glycerate transporter, which is necessary for photorespiration and growth in rice. Copyright © 2020 Shim, Lee, Lee, Brilhaus, Wu, Ko, Lee, Weber and Jeon.Chilling stress can cause cellular DNA damage, affecting the faithful transmission of genetic information. Cold acclimation enhances chilling tolerance, but it is not clear that the process of cold adaption involves DNA damage responses, as cold acclimation does not form real chilling stress. Here we showed with cucumber fruit that pre-storage cold acclimation (PsCA) reduces chilling injury and upregulates DNA damage inducible protein1 (CsDDI1), suggesting that the chilling tolerance induced by cold acclimation involves CsDDI1 transcription. Application of nitric oxide (NO), abscisic acid (ABA) or H2O2 biosynthesis inhibitor before PsCA treatment downregulates CsDDI1 and aggravates chilling injury, while H2O2 generation inhibition plus exogenous NO or ABA application before PsCA treatment restores chilling tolerance, but does not restore CsDDI1 expression, suggesting H2O2 plays a crucial role in triggering cold adaption. CsDDI1 overexpression Arabidopsis lines show faster growth, stronger chilling tolerance, lower reactive oxygen species levels, enhanced catalase and superoxide dismutase activities and higher expression of nine other Arabidopsis defense genes under chilling stress, suggesting CsDDI1 strengthens defenses against chilling stress by enhancing antioxidant defense system. Taken together, CsDDI1 positively regulates chilling tolerance induced by cold acclimation in cucumber. In addition, H2O2 is involved in initiation of cold acclimation. While CsDDI1 upregulation requires H2O2 as a key signaling molecule, the upregulation of CsDDI1 activates an antioxidant system to reduce biotoxic accumulation of H2O2 and helps in DNA repair. Copyright © 2020 Wang, Wang and Zhu.Flowering plants have evolved two distinct clades of chloroplast GrpE homologues (CGEs), which are the nucleotide exchange factor for Hsp70. In Arabidopsis, they are named AtCGE1 (At5g17710) and AtCGE2 (At1g36390). Characterization of their corresponding T-DNA insertion mutants revealed that there is no visible change in phenotype except a defect in protein import in an AtCGE2-knockout mutant under normal growth conditions. However, the embryo development of an AtCGE1-knockout mutant was arrested early at the globular stage. An AtCGE1-knockdown mutant, harboring a T-DNA insertion in the 5'-UTR region, exhibited growth retardation and protein import defect, and its mutant phenotypes became more severe when AtCGE2 was further knocked out. Sub-organellar distribution implied that AtCGE2 might be important for membrane biology due to its preferential association with chloroplast membranes. Biochemical studies and complementation tests showed that only AtCGE1, but not AtCGE2, can effectively rescue the heat-sensitive phenotype of Escherichia coli grpE mutant and robustly stimulate the refolding of denatured luciferase by DnaK. Interestingly, AtCGE1 and AtCGE2 are tending to form heterocomplexes, which exhibit comparable co-chaperone activity to AtCGE1 homocomplexes. Our data indicate that AtCGE1 is the principle functional homologue of GrpE. The possibility that AtCGE2 has a subsidiary or regulatory function through homo- and/or hetero-oligomerization is discussed. Copyright © 2020 Su, Lin and Lai.Bark is a structure involved in multiple physiological functions, but which has been traditionally associated with protection against fire. Thus, little is known about how the morpho-anatomical variations of this structure are related to different ecological pressures, especially in tropical savanna species, which are commonly subjected to frequent fire and drought events. Here we evaluated how the structural and functional variations of bark are related to the processes of resilience and resistance to fire, as well as transport and storage of water in 31 native species from the Brazilian Cerrado. Because of their thick bark, none of the trees analyzed were top-killed after a severe fire event. The structural and functional variations of the bark were also associated with water storage and transport, functions related to properties of the inner bark. In fact, species with a thicker and less dense inner bark were the ones that had the highest water contents in the wood, bark, and leaves. Lower bark density was also related to higher stem hydraulic conductivity, carbon assimilation, and growth. Overall, we provide strong evidence that in addition to protection from fire, the relative investment in bark also reflects different strategies of water use and conservation among many Cerrado tree species. Copyright © 2020 Loram-Lourenço, Farnese, Sousa, Alves, Andrade, Almeida, Moura, Costa, Silva, Galmés, Cochard, Franco and Menezes-Silva.