Abstract
The shoot apical meristem (SAM) is the source of all of the above-ground tissues and organs in post-embryonic development in higher plants. Studies have proven that the expression of genes constituting the WUSCHEL (WUS)-CLAVATA (CLV) feedback loop is critical for the SAM maintenance. Several histone lysine acetylation and methylation markers have been proven to regulate the transcription level of WUS. However, little is known about how histone arginine methylation regulates the expression of WUS and other genes. Here, we report that H4R3 symmetric dimethylation (H4R3sme2) mediated by SKB1/PRMT5 represses the expression of CORYNE (CRN) to maintain normal SAM geometrics. SKB1 lesion results in small SAM size in Arabidopsis, as well as down-regulated expression of WUS and CLV3. Up-regulation of WUS expression enlarges SAM size in skb1 mutant plants. We find that SKB1 and H4R3sme2 associate with the chromatin of the CRN locus to down-regulate its transcription. Mutation of CRN rescues the expression of WUS and the small SAM size of skb1. Thus, SKB1 and SKB1-mediated H4R3sme2 are required for the maintenance of SAM in Arabidopsis seedlings.
Highlights
The shoot apical meristem (SAM) is a self-maintaining structure harboring stem cells which give rise to all of the above-ground tissues and organs in higher plants
We wondered whether the increased expression level of FLOWERING LOCUS C (FLC) in skb1 mutants was responsible for the small SAM size, so we introduced pWUS::GUS and pCLV3::GUS to flc and flc skb1 mutants
We found that the protein arginine methyltransferase SKB1 was functionally involved in the maintenance of SAM in Arabidopsis
Summary
The shoot apical meristem (SAM) is a self-maintaining structure harboring stem cells which give rise to all of the above-ground tissues and organs in higher plants. The stem cells reside at the center of the SAM, known as the central zone (CZ). The PZ is the source of lateral organs, while the RZ gives rise to the pith of stem [1,2,3]. Underlying the CZ, there is a region containing about ten cells termed the organizing center (OC), in which a homeodomain transcription factor WUSCHEL (WUS) is expressed to maintain the number of stem cells [4]. Mature WUS protein migrates to the CZ to activate the transcription of CLAVATA3 (CLV3), which is a marker gene for stem cell identity, by binding to its promoter [6]
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