Abstract

Plant Genomics in China X (Chongqing, August 19 - 21, 2009)

(Submitted on2009-08-01 12:01:22)

Hybridization and Polyploidy-Induced Transcriptomic Response and Epigenetic Changes in Plants

Bao Liu *（刘宝）Key Laboratory of Molecular Epigenetics of MOE, Northeast Normal University, Changchun 130024, China* Phone: 86-431-85099822; e-mail: baoliu@nenu.edu.cn

Inter-specific hybridization polyploidy are common features found in many organismal taxa, and prevails in plants (Otto and Whitton, 2000; Comai 2005; Otto, 2007). Estimates indicate that around 70% of today's angiosperms have experienced one or more episodes of polyploidy in their evolutionary histories, and the majority of which involves hybridization (Wendel, 2000; Liu and Wendel, 2002; Chen et al., 2007). This near ubiquity of hybridization and polyploidy in plant evolution has unequivocally pointed to their great evolutionary potential in this organismal kingdom. However, simple logic would have suggested that the combination of divergent (from different species) genomes into a common nucleus and one-parental cytoplasm may incur incompatibility at multiple levels, which may lead to abnormal development, reduced fitness and reproductive failure -- all these need to be reconciled in a nascent hybrid genome to enable its survival in a short-term basis and evolutionary success from a long-term perspective. Little is known about the means and their underlying mechanisms whereby compatibility at each of these dimensions were accomplished. However, an array of recent molecular and genomic studies in diverse plant systems have begun to shed lights into the mystery of hybridity and polyploidy in plants by revealing that the nascent plant hybrid and polyploid genomes are extremely dynamic, and associated with rapid genomic changes at multiple layers including genetic, epigenetic, transcriptomic and proteomic. These unexpected, non-Mendelian changes may help ameliorate some of the hurdles related to immediate accommodation and establishment in the homoploid hybrid or polyploid organisms, and may provide raw evolutionary materials, and hence, contribute to their long-term evolutionary success (Wendel, 2000; Liu and Wendel, 2003; Adams and Wendel, 2005a, b; Comai, 2005; Chen and Ni, 2006; Chen, 2007; Otto, 2007). To further study gene expression and epigenetic changes associated with hybridization and polyploidy in plants, we employed the Affymetrix microarray platform to analyze transcriptomic responses in an array of novel plant lines derived from wide hybridization and/or genome doubling. We also investigated epigenetic changes in the form of cytosine methylation and its associated transposon activity. To this end, we have made the following major observations: (1) compared with the calculated midparent values or parental mixtures, all studied synthetic allohexaploid wheat lines exhibited transcripts that are deviated from parental additive gene expression. (2) An interesting finding is that the proportions of non-additive transcripts that were shared between any two synthetic allohexaploid lines is very small; nonetheless, the frequencies are significantly higher than expected on a random basis, suggesting a strong effect of genetic context on differential expression of parental transcripts in an allopolyploid genome. (3) A preliminary gene ontology analysis indicates that of the annotated genes that showed non-additive expression in the allohexaploid lines, diverse biological functions were involved such as cellular physiological processes and metabolism, stress response, disease resistance and pathogenesis, among others. (4) Although the number of these genes differ among the three lines, their proportions are very similar, suggesting that the majority of the non-additive expressions in the allohexaploid lines are likely non-stochastic. (5) Physical allocation based on Blast analysis against mapped wheat ESTs indicated that the transcripts exhibiting non-additive expressions distributed throughout the wheat genome. (6) The proportion of non-additive expression genes is much smaller in both number and extent in a pair of reciprocal inter-subspecific (between japonica and indica) rice hybrids and their tetraploids. (7) Even abortive hybridizations between apparently incompatible plant species may cause dramatic changes in transcriptome and transgenerational epigenetic changes, and producing novel phenotypes.

Theme of your abstract: 1. Molecular Marker Assisted Breeding and Genomic Diversity (Chair：Jizeng Jia and Zhikang Li); 2. Functional Genomics (Chair：Qifa Zhang).

Format: Oral speech.

YOUR IP ADDRESS:
38.107.191.117

This site only supports IE, the use of other browsers will lead to error when submit abstract