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Seed germination and photoautotrophic establishment are controlled by the antagonistic activity of the phytohormones gibberellins (GAs) and abscisic acid (ABA). Here we show that Arabidopsis thaliana GAS2 (Gain of Function in ABA-modulated Seed Germination 2), a protein belonging to the Fe-dependent 2-oxoglutarate dioxygenase superfamily, catalyzes the stereospecific hydration of GA 12 to produce GA 12 16, 17-dihydro-16α-ol (DHGA 12 ). We show that DHGA 12 , a C 20 -GA has an atypical structure compared to known active GAs but can bind to the GA receptor (GID1c). DHGA 12 can promote seed germination, hypocotyl elongation and cotyledon greening. Silencing and over-expression of GAS2 alters the ABA/GA ratio and sensitivity to ABA during seed germination and photoautotrophic establishment. Hence, we propose that GAS2 acts to modulate hormonal balance during early seedling development.

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The properties of mucilage obtained from Dioscorea opposita, generated during industrial manufacturing were investigated in this study. Characteristics such as monosaccharide content, amino acid content, molecular weight, and structural features were measured, whereas morphology was observed using a scanning/transmission electron microscope. Additionally, emulsification properties at different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) and under acidic and basic pH (5.0 and 9.0) conditions were studied. The results showed that emulsions prepared from mucilage and medium-chain triglycerides presented more effective emulsifying functions and higher stability, especially at low concentrations. Both, acidic and basic conditions improved the overall emulsification properties, which suggested that the isoelectric point of amino acids may be involved in the emulsification properties. The results of this study show that mucilage from Dioscorea opposita can be considered as a sustainable resource of a natural emulsifier obtained from industrial waste.

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These authors contributed equally to this work. SUMMARYPhotosynthetic electron transport is the major energy source for cellular metabolism in plants, and also has the potential to generate excess reactive oxygen species that cause irreversible damage to photosynthetic apparatus under adverse conditions. Ferredoxins (Fds), as the electron-distributing hub in the chloroplast, contribute to redox regulation and antioxidant defense. However, the steady-state levels of photosynthetic Fd decrease in plants when they are exposed to environmental stress conditions. To understand the effect of Fd down-regulation on plant growth, we characterized Arabidopsis thaliana plants lacking Fd2 (Fd2-KO) under long-term high light (HL) conditions. Unexpectedly, Fd2-KO plants exhibited efficient photosynthetic capacity and stable thylakoid protein complexes. At the transcriptional level, photoprotection-related genes were up-regulated more in the mutant plants, suggesting that knockout Fd2 lines possess a relatively effective photo-acclimatory responses involving enhanced plastid redox signaling. In contrast to the physiological characterization of Fd2-KO under short-term HL, the plastoquinone pool returned to a relatively balanced redox state via elevated PGR5-dependent cyclic electron flow during extended HL. fd2 pgr5 double mutant plants displayed severely impaired photosynthetic capacity under HL treatment, further supporting a role for PGR5 in adaptation to HL in the Fd2-KO plants. These results suggest potential benefits of reducing Fd levels in plants grown under long-term HL conditions.

Rice grassy stunt virus (RGSV) is a tenuivirus posing a threat to rice production in many South, Southeast, and East Asian countries. To date, no host factor interacting with RGSV has been reported. In this study, we screened a rice cDNA library with the GAL4-based yeast two-hybrid system using RGSV p5 as the bait. One of the candidate host factors interacting with RGSV p5 was found to be CBL-interacting protein kinase 25 (OsCIPK25), a member of the plant-specific CBL-CIPK Ca signaling network. The interaction between RGSV p5 and OsCIPK25, as well as OsCIPK5, which is closely related to OsCIPK25, was confirmed by their cellular co-localization and by a bimolecular fluorescence complementation assay in Nicotiana benthamiana cells. Given the importance of CIPKs in the regulation of ion homeostasis and the resemblance of RGSV symptoms to potassium deficiency in rice, we evaluated potassium content of RGSV-infected rice and found it to be much lower than that in the healthy rice.

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