| Turfgrass plays a more and more important role in beautifying the environment in which people live,maintaining a relatively ecological balance,and social and economic development.Drought and water shortage hinder the growth of turfgrass and limit its further development and application.Ryegrass is a cold-season turfgrass widely grown.Therefore,studying the drought resistance of ryegrass plays an important role in its genetic improvement and water-saving irrigation,and can also be used to guide the establishment,management and maintenance of ryegrass.Under drought stress,the ryegrass LpXTH8 gene was induced to express.Because of the difficulties in carrying out functional studies in ryegrass,the homologous gene BdXTH27 in Brachypodium distachyon,a model plant closely related to ryegrass,was selected to assist in the study.Using ryegrass and Brachypodium distachyon(wild type and mutant)as experimental materials,potted seedlings of ryegrass and Brachypodium distachyon were subjected to natural drought treatment in the greenhouse,and samples were taken every 3days,to determine various physiological and biochemical indexes of ryegrass and Brachypodium sibiricum under drought stress,as well as changes in gene expression of xyloglucan endoglycosidase / hydrolase gene;explore the function of BdXTH27 gene in plant growth and development;making further analysis of the resistance regulation mechanism of ryegrass and Brachypodium distachyon to drought stress from the level of physiological,biochemical and molecular biology,it provides a theoretical basis for the genetic improvement of ryegrass drought resistance and its wide application in landscaping.The test results are as follows:(1)The soil water content of ryegrass continued to decrease during drought stress.On the 12 th day,the root system of the plant was severely lignified and browned.The root vitality of the plant showed a decreasing trend with the increase of drought.In the early stage of water stress,the chlorophyll content in ryegrass leaves increased,and the chlorophyll was degraded when the stress reached a certain level,and the content continued to decrease.The electrical conductivity of the leaves continued to increase with the increase of the degree of drought stress,and rose to the highest on the 12 th day.At this time,the plants were seriously injured and the leaves appeared wilted.(2)During drought stress,the activities of the three protective enzymes SOD,POD and CAT in the ryegrass antioxidant system generally showed a trend of increasing first and then decreasing.At the later stage of the treatment,the activities of the three enzymes decreased,indicating that the antioxidant enzymes have limited ability to regulate drought stress.The content of malondialdehyde(MDA)increased continuously with the intensification of drought stress,and reached the highest level on the 12 th day of drought.(3)Drought stress caused an increase in the content of proline,soluble sugar,and soluble protein in ryegrass leaves.Proline content increased significantly after 12 days of treatment,indicating that the membrane system of the plant was seriously damaged at this time.Drought can induce the expression of LpXTH8 gene in ryegrass,and the expression level continues to increase with the increase of drought stress,and the expression level reached the highest on the 12 th day.(4)The roots of the Brachypodium distachyon mutant plants are thinner and generally longer than the wild type,with significant differences.The angle between the leaves of the mutant plants at the seedling stage becomes larger and the height is lower than that of the wild type.By observing the paraffin sections of the wild type and mutant roots,it was found that the mutant roots were thinner than the wild type due to the decrease in the number of lateral cortical cell wall cells,and the increase in root length was caused by the longitudinal cell elongation.(5)Tissue-specific expression analysis showed that the expression of BdXTH27 gene was highest in the root,and the expression level of other organs was very low.After p BdXTH27::GUS staining,the root of the plant was stained the deepest.The above two results together confirmed that BdXTH27 gene is mainly expressed in the root.The p ZP211:BdXTH27-GFP vector was constructed to transiently infect tobacco leaves and onion epidermis,and it was found that the BdXTH27 gene of Brachypodium distachyon is located on the cell wall.(6)Under drought stress,the activities of SOD,POD,and CAT of Brachypodium distachyon mutants were higher than those of wild type.SOD activity increased first and then decreased,but the change trend of POD and CAT enzyme activities was not obvious.The content of mutant and wild-type MDA increased with the increase of drought,but the mutant was lower than that of wild-type.(7)Under drought stress,the content of proline,soluble sugar and soluble protein in the mutant of Brachypodium distachyon was higher than that of wild type.The content of proline and soluble sugar increased with the increase of treatment time,and the content of soluble protein did not change significantly.Therefore,the mutant may produce more osmotic adjustment substances during drought stress to reduce the damage caused by drought stress. |
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