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Open Access Highly Accessed Research article

Global transcriptome analysis reveals distinct expression among duplicated genes during sorghum-Bipolaris sorghicola interaction

Hiroshi Mizuno1, Hiroyuki Kawahigashi1, Yoshihiro Kawahara1, Hiroyuki Kanamori1, Jun Ogata1, Hiroshi Minami2, Takeshi Itoh1 and Takashi Matsumoto1*

Author affiliations

1 National Institute of Agrobiological Sciences (NIAS), Agrogenomics Research Center, 1-2, Kannondai 2-chome, Tsukuba, Ibaraki 305-8602, Japan

2 Mitsubishi Space Software Co. Ltd, Takezono 1-6-1, Tsukuba, Ibaraki 305-0032, Japan

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Citation and License

BMC Plant Biology 2012, 12:121  doi:10.1186/1471-2229-12-121

Published: 29 July 2012

Abstract

Background

Sorghum (Sorghum bicolor L. Moench) is a rich source of natural phytochemicals. We performed massive parallel sequencing of mRNA to identify differentially expressed genes after sorghum BTx623 had been infected with Bipolaris sorghicola, a necrotrophic fungus causing a sorghum disease called target leaf spot.

Result

Seventy-six-base-pair reads from mRNAs of mock- or pathogen-infected leaves were sequenced. Unannotated transcripts were predicted on the basis of the piling-up of mapped short reads. Differentially expressed genes were identified statistically; particular genes in tandemly duplicated putative paralogs were highly upregulated. Pathogen infection activated the glyoxylate shunt in the TCA cycle; this changes the role of the TCA cycle from energy production to synthesis of cell components. The secondary metabolic pathways of phytoalexin synthesis and of sulfur-dependent detoxification were activated by upregulation of the genes encoding amino acid metabolizing enzymes located at the branch point between primary and secondary metabolism. Coordinated gene expression could guide the metabolic pathway for accumulation of the sorghum-specific phytochemicals 3-deoxyanthocyanidin and dhurrin. Key enzymes for synthesizing these sorghum-specific phytochemicals were not found in the corresponding region of the rice genome.

Conclusion

Pathogen infection dramatically changed the expression of particular paralogs that putatively encode enzymes involved in the sorghum-specific metabolic network.