Abstract
Macrosclereid cells, which are a layer in the seed coat of Medicago truncatula, accumulate large amounts of phytochemicals during their development. But little is known about the complex and dynamic changes during macrosclereid cell development. To characterize the phytochemicals and the related gene expression during the development of M. truncatula macrosclereid cells, a high performance liquid chromatography-mass spectrometry (HPLC-MS) assay and microarray study were conducted on transcriptome changes from macrosclereid cell during seed development. A total of 16 flavonoids by HPLC-MS and 4861 genes exhibited significant differences at transcript levels by microarray analysis were identified for macrosclerid cells at six different time points during seed development. 815 abiotic and biotic stress genes, 223 transcriptional factors (TFs), and 155 annotated transporter proteins exhibited differential expression during the development of macrosclereid cells. A total of 102 genes were identified as involved in flavonoid biosynthesis, phenypropanoid biosynthesis, and flavone and flavonol biosynthesis. We performed a weighted gene co-regulatory network (WGCNA) to analyze the gene-flavonoid association and rebuilt the gene regulatory network during macrosclereid cell development. Our studies revealed that macrosclereid cells are, beside as the first barrier of defense against diseases, an excellent model system to investigate the regulatory network that governs flavonoid biosynthesis.
Highlights
Our studies revealed that macrosclereid cells are, beside as the irst barrier of defense against diseases, an excellent model system to investigate the regulatory network that governs lavonoid biosynthesis
Under 500x magniication, we found that the seed coat epidermis, which will develop into MC in the later developmental stages, is the major site of phenolic compound biosynthesis and accumulation (Fig. 2)
Phenolic compounds were observed in small vacuoles (Fig. 2A) of epidermis cells from the seed coats of developing M. truncatula pods at 6 days post pollination (DPP)
Summary
Macrosclereid cells, which are a layer in the seed coat of Medicago truncatula, accumulate large amounts of phytochemicals during their development. Few studies have focused on the development of M. truncatula MC (MC), which are a specialized cell layer in the seed coat[10]. Several key genes involved in seed coat diferentiation and proanthocyanidin (PA) biosynthesis regulation have been identiied and characterized through studies of Arabidopsis seed coat mutants, and the PA biosynthetic pathway has been largely elucidated[14, 16,17,18]. Our studies indicated that TFs and structural genes involved in regulation the accumulation of lavonoid compounds in MC. he results of this study provide some insight into the distinct chemistry of developing MC
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