Transcriptome Analysis Reveals a Critical Role ofCHS7andCHS8Genes for Isoflavonoid Synthesis in Soybean Seeds

Abstract

We have used cDNA microarray analysis to examine changes in gene expression during embryo development in soybean (Glycine max) and to compare gene expression profiles of two soybean cultivars that differ in seed isoflavonoid content. The analysis identified 5,910 genes that were differentially expressed in both soybean cultivars grown at two different locations for two consecutive years in one of the five different stages of embryo development. An ANOVA analysis with P value , 0.05 and , 0.01 indicated that gene expression changes due to environmental factors are greater than those due to cultivar differences. Most changes in gene expression occurred at the stages when the embryos were at 30 or 70 d after pollination. A significantly larger fraction of genes (48.5%) was expressed throughout the development and showed little or no change in expression. Transcript accumulation for genes related to the biosynthesis of storage components in soybean embryos showed several unique temporal expressions. Expression patterns of several genes involved in isoflavonoid biosynthesis, such as Phenylalanine Ammonia-Lyase, Chalcone Synthase (CHS) 7, CHS8, and Isoflavone Synthase2, were higher at 70 d after pollination in both the cultivars. Thus, expression of these genes coincides with the onset of accumulation of isoflavonoids in the embryos. A comparative analysis of genes involved in isoflavonoid biosynthesis in RCAT Angora (high seed isoflavonoid cultivar) and Harovinton (low seed isoflavonoid cultivar) revealed that CHS7 and CHS8 were expressed at significantly greater level in RCAT Angora than in Harovinton. Our study provides a detailed transcriptome profiling of soybean embryos during development and indicates that differences in the level of seed isoflavonoids between these two cultivars could be as a result of differential expression of CHS7 and CHS8 during late stages of seed development.

Using Genomics to Study Legume Seed Development

“…Currently, Medicago, Lotus, and soybean cDNA and oligonucleotide microarrays are available (Endo et al, 2002;Vodkin et al, 2004;Firnhaber et al, 2005). An increasing collection of legume seed transcriptome and proteomic data (Thibaud-Nissen et al, 2003;Firnhaber et al, 2005;Hajduch et al, 2005;Buitink et al, 2006;Dhaubhadel et al, 2007), cDNA library collections, and public EST databases (Journet et al, 2002;Shoemaker et al, 2002;Asamizu et al, 2004;Firnhaber et al, 2005;Ramirez et al, 2005) have helped to provide a global view of gene activity at specific seed developmental stages. Sequences of the Medicago, Lotus, soybean, common bean, and peanut genomes (Broughton et al, 2003;Gepts et al, 2005;Young et al, 2005;Jackson et al, 2006) should provide an invaluable resource for identifying and characterizing genes that play critical roles during seed and embryo development in the near future.…”

Augmentation of major isoflavones in Glycine max L. through the elicitor-mediated approach

“…As suggested by earlier reports, the use of methyl jasmonate might activate the respective genes in the phenylpropanoid (PP) pathway (DIXON and PAIVA 1995). The varied expression of IFS genes (IFS1 and IFS2) is responsible for the changes in level of isoflavones in seeds under elicitor treatment (DHAUBHADEL et al 2007, CHENG et al 2008. Also, yeast extract elicited the accumulation of isoflavones via elevated level of L-phenylalanine ammonia lyase and chalcone synthase transcripts in cell suspension of Medicago truncatula (SUZUKI et al 2005) and transcripts of flavanone 2-hydro-xylase, isoflavone 2'-hydroxylase, and isoflavone synthase in Glycyrrhiza echinata cell suspension cultures (NAKAMURA et al 1999).…”

Maturation of somatic embryos as a model for soybean seed development

“…The similarity of somatic embryos to seeds may thus be lost at the late stages of maturation. However, transcriptome and proteome analyses of developing soybean seeds have indicated that many, but not all, genes involved in the production of seed components, including storage reserves and secondary metabolites, are expressed from an early stage of seed development (Hajduch et al 2005;Dhaubhadel et al 2007). Transcripts of such genes were also detected by microarray analysis of somatic embryos (Thibaud-Nissen et al 2003).…”