| Caragana korshinskii Kom. is a xerophyte shrub widely distributed in the Loess Plateau,with ideal economic benefits for forage utilization and environmental benefits for“Grain for Green”. Previous research on drought resistance mostly concentrated in geographical distribution, physiological and ecological characteristics of C. korshinskii, as well as photosynthesis and transpiration, taxonomy and morphology anatomy, but drought tolerance mechanism in C. korshinskii is still unclear. In the present study, in order to better understand the tolerance mechanisms to drought stress in C. korshinskii, intensive study of the expression patterns of many stress-related genes were urgently required. Here, we report the expression profiling of leaf transcriptome of C. korshinskii under different water stress, which helped identify stress-related candidate genes and gene regulatory networks for future screening.Combined with the change of anatomy and physiology indicators of leaf in C. korshinskii, the data obtained will be served as an invaluable reference to further our knowledge about the tolerance mechanism to drought in C. korshinskii at the molecular level.(1) To identify differentially expressed genes in response to drought, 2 DGE libraries have been generated from Huangling and Yulin samples. 7,998 differentially expressed genes(DEGs) were identified, 3,660 genes are down-regulated and 4338 genes are up-regulated.Based on analysis of differentially expressed genes, metabolic processes are significantly effected. Due to the changes in the metabolic process will affect the synthesis of metabolites,normal transport of metabolites was closely related with vascular tissues. The results showed that metabolism related with lignin formation, such as phenylalanine metabolism and related secondary metabolism, was significantly affected. The synthesis of lignin was better for water transporting and resistance to adverse environmental. The analysis showed that the gene expression increased, which were involved in the development of vascular tissues.(2) Morphology and anatomy of the leaf veins were analyzed. The results show that with the drought increasing, vein density of C. korshinskii increased, veinlets is more developement; number of veins bundle sheath cells raised, as well as bundle sheath cell area.Cross-sectional area and the total area of vascular bundles of petiole became larger, the thickness of phloem and xylem in vascular increased under drought stress. The number ofchloroplasts in mesophyll cells have risen, the shape connected all chloroplast was closed to a circle. The size and the number of starch grain were gradually increasing with increased drought.(3) The leaf characteristics and gas exchange characteristics of C. korshinskii were studied. It showed that stomatal conductance(gc) decreased, while the intercellular CO2concentration(Ci) increased. Net photosynthetic rate(An) increased rapidly firstly, and remained at a high level. It was indicated that even in the Shenmu, where was not with enough precipitation, stomatal aperture was sufficient to absorb CO2, which led to leaf mass per area had an increasing. The decreasing of stomatal aperture didn’t affect the photosynthetic obviously, but transpiration of C. korshinskii reduced. It caused the water use efficiency(WUEi) increase significantly. High An and WUEi was contribute to accumulate carbon assimilation, organic carbon content and density increased, thereby the total biomass of C. korshinskii raised undoubtly.(4) The organic carbon content and biomass of Caragana korshinskii Kom. and locust grew in the same conditions were analyzed, it shows that organic carbon content of C.korshinskii was significantly higher than locust. The biomass of branches in C. korshinskii and locust are in the largest proportion, indicating that branches is the main organization of plant organic carbon and biomass allocation, but the total biomass and organic carbon density of locust wan higher than C. korshinskii. |
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