A histone methyltransferase, EARLY FLOWERING IN SHORT DAYS (EFS) is required for reproductive organs development via histone H3K36 methylation in the oil-seed type Brassica rapa (B. rapa var. trilocularis) plant

초록

Histone methylation modifies the epigenetic context of target genes to modulate gene expression. EFS (EARLY FLOWERING IN SHORT DAYS) catalyzes the H3K36me3 on target chromatin in Arabidopsis. Arabidopsis EFS plays a crucial role in many aspects of growth and development, thus loss-of-function mutants of EFS, efs exhibits various developmental defects. However, functional role of B. rapa homolog of Arabidopsis EFS, BrEFS is merely investigated. In this study, we isolated a mutant, named as 'brefs' from the EMS-treated oilseed-type B. rapa (B. rapa var. trilocularis) mutant population. Comparative sequencing analysis showed that BrEFS (Bra015678) contains a premature stop codon in the coding sequence of BrEFS in brefs mutant. The 'brefs' mutant exhibited developmental defects such as smaller leaf, short plant height, wavy petal, and abnormal pollen and seeds. Complementation assay with BrEFS transgene into Arabidopsis efs-3 mutant showed that BrEFS is authentic homolog of EFS in Brassica rapa. To reveal the functional role of BrEFS, we performed transcriptomic analysis between wild type and 'brefs' mutant. In addition, Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) showed that enrichment of H3K36me3 histone mark on WUS, NST1, IAA19, and MIF2 genes involved in flower organ development were significantly compromised in the 'brefs' mutant compared to wild type. Therefore, it was concluded that BrEFS plays an important role in the regulation of flower organ development genes by depositing H3K36me3 on these target genes. Taken together, we showed that BrEFS is required for the proper epigenetic control of developmental program, particular reproductive organs development in B. rapa plant. Development of floral organs of plants is very important for agricultural productivity. This is because it directly affects the reproduction, fruits, quality, and yield of crops. In addition, understanding of flower development can affect future crop varieties improvement and productivity increase.

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