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Title: Transcriptional regulatory programs underlying barley germination and regulatory functions of Gibberellin and abscisic acid

item An, Yong-Qiang - Charles
item LIN, LI - University Of Massachusetts

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2011
Publication Date: 6/13/2011
Citation: An, Y., Lin, L. 2011. Transcriptional regulatory programs underlying barley germination and regulatory functions of Gibberellin and abscisic acid. Biomed Central (BMC) Plant Biology. 11:105.

Interpretive Summary: Germination attracts the attention of barley researchers due to its economic importance to the malting industry and barley growers. Malting industries utilize the germination process to turn the storage proteins and starch in barley grains into amino acids and sugars for brewing. Improper germination during grain harvest and storage could lead to significant economic damage for barley growers due to loss of premium price. To understand the molecular mechanism underlying seed germination and to isolate the genes important to seed germination, we used GeneChip technology to simultaneously determine expression patterns of over 22,000 genes during the course of seed germination. We observed that expression of 5382 genes increased or decreased during barley germination. We used a variety of computer software to reveal that the molecular expression program composed of three distinct phases, and each phase induced a specific set of metabolic pathways and genes. The studies also provide insight into the molecular mechanism on how two phytohormones, GA and ABA, regulate seed germination by comparing the genes regulated by germination, GA and ABA. Thus, our research generated an understanding of the molecular mechanism underlying seed germination and identified genes and molecular functions related to seed germination. This understanding and identified genes are valuable for maltsters to improve the malting process and for barley breeders to develop barley varieties with pre-harvest spouting resistance and superior malting qualities.

Technical Abstract: Barley germination is a complex and multi-stage biological process important to plant development, plant evolution, and agricultural production. It is accompanied with concerted expression of many genes and biological pathways. Transcriptomic analysis of barley grains/seedlings representing six well characterized and distinct germination stages revealed that transcriptional regulatory program of barley germination composed of pre-, trans-, and post-germination phases. Each of the germination phases was accompanied with transcriptional induction or suppression of distinct biological pathways and gene families. The cell wall synthesis and the regulatory components including transcription factors, signaling components and post-translational modification proteins were specifically and transiently up-regulated in early pre-germination phase while histone gene families and many metabolic pathways including amino acid synthesis, protein degradation were up-regulated in trans-germination phase. Photosynthesis and storage reserve mobilization pathways were induced in post-germination phase. Interestingly, stress related pathways were suppressed through the entire course of seed germination. In comparison with transcriptomes of barley aleurone in response to gibberellins (GA) and abscisic acid (ABA), we observed that germination responsive genes were preferred to be coordinately regulated by GA and antagonistically regulated by ABA. It provided strong evidence at systems levels that GA enhances and ABA suppresses seed germination. Major CHO metabolism, cell wall degradation and protein degradation pathways were up-regulated by both GA and seed germination, are likely to be important part of pathways mediating GA regulation of seed germination. The studies provide a great insight into gene regulatory networks underlying barley seed germination and GA and ABA regulation of seed germination, and establish a systems platform for future seed germination research.