Molecular Biology Study On Responses To Temperature And Photoperiod In Wheat Development

Temperature and photoperiod are most important environment factors which impact the wheat transformation from vegetative phase to reproductive phase, and flowering. Venalization and photoperiod characteristics of wheat influence the cultivar regionalization, introduction and domestication as well as cultivation techniques. The vernalization and photoperiod characters are that wheat satisfy the low temperature and long photoperiod requirement during wheat flowering.This study characterized allele composition of the different vernalization genes in different kinds of wheat development type by using the specific molecular makers, and analyzed the correlationship between vernalization gene composition and wheat development traits. We also dissected the transcriptome profile and digital gene expression profile of wheat buds during vernalization process by using high-throughput second generation sequencing technique. The gene network involved in the vernalization process was explored. The key results are as follows:1. Total of200Chinese wheat cultivars were used to analyze the vernalization gene composition of Vrn-A1, Vrn-B1, Vrn-D1and Vrn-B3. The results showed that all cultivars carry the recessive allele at Vrn-A1and Vrn-B3loci. The dominant proportion was18%at Vrn-B1locus. At Vrn-D1loci,83of200wheat cultivars were detected as a dominant gene, and the remaining117cultivars were the recessive gene. Fifty four of83dominant cultivars were Vrn-D1a type and there were29Vrn-D1b cultivars. There were38dominant cultivars (41.8%) and53recessive cultivars (58.2%) in Vrn-D1loci in the Yellow and Huai River Valleys Facultative Wheat Zone. Four cultivars were firstly detected a174bp transposon insertion in Vrn-Dl promoter region of, in117recessive materials, named Vrn-D1c type and the remaining113cultivas were vrn-D1type. Vrn-D1a can be labeled as an effective semi-weak spring and winter wheat molecular marker in the Huang-huai wheat area.2. Coding regions of six genes, i.e. ZCCT-A1/A2, ZCCT-B1/B2and ZCCT-D1/D2and16,35and39mutations located in43amino acids CCT conserved regions were analyzed by RT-PCR in six cultivars with different vernalization characters. The results showed that there were difference among these cultivars in CCT functional domains ZCCT-A1. Feimai carried R35W mutation while Liaochun10, Zhengmai9023, Zhoumai18, Yumai49-198, Jing841Cultivar possess R39C mutation. All tested cultivars were R16C mutation in ZCCT-A2locus while there was no mutation in B and D genome. The results showed that A genome have allelic variation in Vrn2gene coding region, and B, D genome genes in the tested varieties are dominant. Six cultivar promoters were cloned and there were3SNP in both ZCCT-A1and ZCCT-D1promoter. There were3TCT repeats in the97bp upstream of promoter in5cultivars except Zhengmai9023. Two tandem TCT sequences were identified in a97bp upstream of the ZCCT-B1promoter in6cultivars and the TCT missing can be used as molecular markers for ZCCT-B1locus.3. Spring wheat cultivar Liaochun10and winter cultivar Jing841were used for transcriptional profiling and expression profiling analysis. Jing841showed a much stronger response to vernalization than the spring cultivar Liaochun10. Total of14648upregulated genes and15240down-regulated genes were identified and analyzed by GO functional annotation. Many cellular processes, metabolic processes, stress response, signal transduction, ion binding activity catalytic activity transporter protein genes were found involved in vernalziation process. The expression profiles were verificated by semi-quantitative RT-PCR and real-time quantitative RT-PCR, which showed consistant results with digital gene expression. KEGG analysis showed that biosynthesis of secondary metabolites, plant hormone signal transduction, plant-pathogen interaction pathways, and other starch and glucose metabolism pathway were involved in the wheat vernalization process.4. Fifteen wheat cultivas from different Chinese ecological zones countrywide were used to study relationship between seedlings-heading time and photoperiod conditions. The results showed a linear regression between seedling-heading stage and lighting hours in wheat. According to the coefficient of variation seedlings-heading under different light conditions, wheat cultivars can be divided into photoperiod sensitive cultivars and photoperiod insensitive cultivars. Vernalization and photoperiod response interactions exist in most cultivars. Twelve of15cultivars unvernalized could not flowering in the artificial climate chamber.5. Photoperiod sensitive cultivar Ningchun36and photoperiod-insensitive cultivar Liaochun10were used for photoperiod sensitivity analysis in different wheat apical development stage. Results showed that photosensitivity difference of Ningchun36and10Liaochun was mainly determined by the Ppd-D1locus. Double range and followed stages were major developmental stages that differentiate photoperiod sensitive cultivars and photoperiod insensitive cultivars. The24hour photoperiod key genes expression pattern showed that photoperiod genes TaGI, TaCO were not regulated between photoperiod sensitive cultivars and photoperiod insensitive cultivars. Flowering difference between photoperiod sensitive and insensitve cultivar was manily regulated by TaFT.