Transcriptomic Responses of Garlic(Allium sativum L.)to Heat and Drought Stresses

Heat and drought are prominent abiotic stressors that limit crop productivity and yield,particularly concerning climate change;therefore,understanding the molecular mechanisms underlying plant stress responses is crucial for stress-tolerant crop production.This study conducted a transcriptomic analysis to elucidate how garlic(Allium sativum L.)responds to drought and heat stress conditions.Transcriptome libraries were generated to identify differentially expressed genes(DEGs)induced by drought and heat stresses.Functional classification and clustering analysis of DEGs revealed stress-specific gene expression patterns.Notably,cell wall-related genes were implicated in the drought response,whereas heat stress was associated with heat stress transcription factors and heat shock proteins.Our results provide essential information for future studies on stress tolerances in garlic.

Photosynthesis,Metabolite Composition and Anatomical Structure of Oryza sativa and Two Wild Relatives,O.grandiglumis and O.alta

Photosynthesis, enzyme activities and metabolite pools associated with primary carbon metabolism in leaves were studied in O. grandiglumis and O. alta （wild relatives of rice which produce high biomass） versus O. sativa （a japonica cultivar and a indica-japonica hybrid） to assess their potential for identifying traits which might be utilized to enhance rice productivity. The wild relatives had higher rates of photosynthesis on a fresh weight basis, and higher water use efficiency than the O. sativa lines. There were no striking differences in activities of a number of key enzymes in carbon and nitrogen metabolism between the wild relatives and cultivated rice lines. Along with higher rates of photosynthesis on a fresh weight basis, the leaves of the two wild species had higher nitrate content, higher levels of starch, glucose and fructose, and higher levels of organic acids （malate, succinate and acetate）, compared to the O. sativa lines. The results suggested that O. grandiglumis and O. alta have differences in physiology and primary metabolism which might be exploited to improve growth and productivity of cultivated rice.

Arabidopsis thaliana RECEPTOR DEAD KINASE1 Functions as a Positive Regulator in Plant Responses to ABA

Abscisic acid （ABA） is a major phytohormone involved in important stress-related and developmental plant processes. Membrane-delimited ABA signal transduction plays an important role in early ABA signaling, but the molecular mechanisms connecting core signaling components to the plasma membrane remain un- clear. Plants have evolved a large number of receptor-like kinases （RLKs） to modulate diverse biological processes by perceiving extracellular stimuli and activating downstream signaling responses. In this study, a putative leucine-rich repeat-RLK gene named RECEPTOR DEAD KINASE1 （AtRDK1） was identified and characterized in Arabidopsis thaliana. RDK1 promoter-GUS analysis revealed that RDK1 is expressed ubiq- uitously in the various tissues in Arabidopsis, and its expression is mainly induced by ABA. In the presence of ABA, RDKl-deficient rdkl-1 and rdkl-2 lines showed significant resistance in cotyledon greening and root growth, whereas RDKl-overexpressing lines showed enhanced sensitivity. Consistently, the expres- sion of ABA-responsive genes was significantly downregulated in rdkl mutant seedlings, which were also hypersensitive to drought stress with increased water loss. Interestingly, RDK1 was found to be an atypical kinase localized to the plasma membrane and did not require its kinase activity during ABA-mediated inhi- bition of seedling development. Accordingly, RDK1 interacted in the plasma membrane with type 2C protein phosphatase ABSClSIC ACID INSENSITIVE1 （ABI1）; this interaction was further enhanced by exogenous application of ABA, suggesting that RDKl-mediated recruitment of ABI1 onto the plasma membrane is important for ABA signaling. Taken together, these results reveal an important role for RDK1 in plant responses to abiotic stress conditions in an ABA-dependent manner.