| Catalpa bungei, one of the endemism and valuable timber tree species in China, whichhas been cultivation more than2600years. This species was widely distribution in China andprimarily be used as the raw materials of high-end furniture and musical instruments cause ofthe excellent material quality. However, the recently promotion main cultivar has been shown adiscrepancy drought resistance, the performance was misadventure under the relativelydroughty condition. Therefore, how to selection breeding the excellent new varieties withrelatively drought-tolerant and high water use efficiency has become an important orientationfor improvement the mass growth of Catalpa bungei under the relatively droughty condition.Understanding the physiological and molecular response mechanism to drought stress andmining the key genes in Catalpa bungei is the foundation of effective breeding. This studychoose the excellent drought resisting clone of Catalpa bungei as test materials, usinghigh-throughput sequencing technology to build the assemblage of transcription, adopting thegene chip technology to excavate the key response gene after drought treatment, combinedwith the physiological changes to elaborate the response mechanism. The main results were asfollows:（1）In the process of natural drought stress, the height, diameter and leaf growth basicallystopped when the gravimetric water content drop to23%, the leaf area of mature leaves was53%of that under normal conditions（93.5cm2）. Net photosynthetic rate （Pn）and photosyntheticperformance index（PI）decreased significantly, Pn was close to0when the soil moisturecontent down to15%, no significant change in the efficiency of light energy conversion（Fv/Fm）. The content of free proline, soluble sugar, abscisic acid in leaves and roots weresignificantly elevated under drought stress treatment, the content of jasmonic acid was slightlyincreased, the content of soluble protein was firstly increased and then decreased; the activity of SOD, POD in leaves and roots and leaf POD activity were shown a trend of decline at firstand significantly increased in late.（2）Leaves, roots, stems, and other tissue of three Catalpa bungei genotypes which undernormal and drought stress treatment were acquisition and mixed for transcriptome sequencing（454pyrosequencing）, a total of77,337unigene were obtained, Clustering with NR database,a total of33,672unigene have been found homologous sequences, among which19,110acquired GO functional annotation.250metabolic pathways including Carbohydrate, Aminoacid, fatty acid metabolism, Photosynthesis, citrate cycle, glycolysis were got by KEGGmetabolism pathways enrich.2,782SSR including double-nucleotide repeat（Di-）to six baserepeat （Hexa-）, and mixed type were explored, a total of79,528SNP were excavated.（3）Based on the transcriptome sequencing results, expression profile chip were designed.According to the growth and physiological change trends under drought stress treatment,5soilmoisture gradient（including controls）were chosen to analysis the gene differences expressionin leaves and roots. Comparing with the control, totally16,137differentially expressed genes inleaves and14,913in the roots were discovered under four kinds of drought stress treatments.2,233genes in leaves were commonly differentially expression under the four drought stresstreatments, including630genes（continuous differential gene）have the trend of increasing ordecreasing expression quantity with the drought stress degree increased;1,006genes in rootswere commonly differentially expression under the four drought stress treatments, including230genes（continuous differential gene）have the trend of increasing or decreasing expressionquantity with the drought stress degree increased; results of GO and KOG annotation of thecontinuous differential gene in leaves and roots showed that the differential gene in leaves androots were mainly involved in signal transduction pathway, transcription, transmembrane iontransport, osmotic adjustment substances sythesis, antioxidant enzyme and hormone sythesisother functions and processes.（4）According the functional analysis, the droughts stress response-related genes wereexplored, including four aspects. Signal transduction related genes: Serine/threonine-protein kinase, leucine-rich repeat（LRR）receptor-like protein kinase, MYB, MYC, bZIP, NAC;Antioxidant protective enzyme gene: NADPH（protochlorophyllide oxidoreductase）,glutathione peroxidase（GSH-Px）, manganese superoxide dismutase（Mn-SOD）, S-adenosyl-L-methionine（△24-sterol-C-methyltransferase）, type II peroxiredoxin（POD）, butyrate-theCoA ligase AAE11;Adjustment substances synthesis related gene: sucrose synthase, sucrose phosphatesynthase, Raffinose synthase, and stachyose synthase,△1-pyrroline-5-carboxylate synthase,ornithine-△-aminotransferase, pyrroline-5-carboxylate reductase, glutamate dehydrogenase,aldehyde dehydrogenase, choline monooxygenase;Hormone synthesis related genes:9-cis-epoxycarotenoid dioxygenase（NCED）, ABAaldehyde oxidase, cytochrome P450, gibberellin20-oxidase,12-oxophytodienoic acid10,10-reductase. The differential expression gene above-mentioned were the molecular basis ofCatalpa bungei clones2-8respond to drought stress, the mining and function analysis of suchgene have supported for the selection and breeding of superior drought resistant Catalpabungei clones... |
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