Mongolicus Germplasm Resources With Drought-resistant Gene

As the only evergreen broad-leaf shrub in the northwestern desert of China, Ammopiptanthus mongolicus shows very strong resistance to drought and cold. In order to explore the physical and molecular mechanisms underlying the drought tolerance in A. mongolicus, we analyzed physiological and biochemical characteristics in A. mongolicus seedling under drought stress. We performed large-scale transcriptome sequencing of A. mongolicus root using Roche/454next-generation sequencing technology; and the drought responsive genes of A. mongolicus differentially expressed under drought treatment were identified by further quantitative real-time PCR analysis. The results are discussed as follow:The RWC, MDA and REL in the leaf of A. mongolicus seedling did not change compared with control under treatment of20%PEG6000for1h-72h. After24h drought stress, RWC of the root of A. mongolicus seedling decreased significantly, while MDA and REL increased. The proline accumulated abundantly in both leaves and roots of A. mongolicus after6h drought stress. In the drought condition, the activities of SOD, CAT and POD in A. mongolicus seedling were distinctly regulated. In leaves of A. mongolicus seedling, the activity of SOD was down regulated at first then increased; the activity of CAT decreased gradually, but the POD increased a little at6h drought treatment. In the root, the activities SOD, CAT and POD were all up regulated, among which SOD and POD increased the most. These results indicated that the physical responses were different in leaves and roots of A. mongolicus and the response of root was more intense, after watering root with20%PEG6000.The transcriptome of A. mongolicus root obtained672,002HQ reads from a454GS XLR70Titanium pyrosequencer, and the average length was279bp. The672,002preproeessed sequencing reads were assembled into27,366unique sequences including14,912contig and12,454singlets, which total length was approximately14Mb. Gene ontology assignments were used to classify the functions of the A. mongolicus transcripts, and the9,771annotated sequences can be categorized into3functional groups:biological process, cellular component, and molecular function. To identify drought responsive genes,27unigenes were selected from the unique sequences classified in GO categories by qRT-PCR technology. When the expression models were analyzed with the root of the A. mongolicus treated by20%PEG6000,27genes were identified and categorized into4groups by the stress they responsed to, namely osmotic stress, oxidative stress, hormone stimulus and light stimulus. A gene was difined as the drought stress induced gene if it was up-regulated under1h and72h stress and the relative expression exceeded2-fold change.4 genes we obtained met such a definition, coding glycoside hydrolase family2protein, peroxidase superfamily protein, GPX3and phototropic-responsive NPH3family protein; A gene was difined as the drought stress inhibited gene if it was down-regulated under1h and72h stress and the relative expression did not exceed0.8-fold change.4genes we obtained met such a definition, coding ERD14, SULTR1;3, thioredoxin family protein and phototropic-responsive NPH3family protein. This study facilitated the research on drought resistance mechanism and related genes in A. mongolicus.