4/25/2023 0 Comments Srdx motifGain-of-function experiments have also been performed to assess the ability of ATML1 to promote epidermal cell differentiation. Considering that the epidermis is the first tissue formed during embryogenesis, the epidermis formation might be a prerequisite for the proper progression of embryogenesis. These results revealed that ATML1 and PDF2 are required for proper embryo development as well as epidermal specification. The outermost cells of the arrested atml1 pdf2 embryos were swollen and often underwent unusual periclinal cell divisions, suggesting that epidermal cell identity was lost in those embryos. After 11 years, atml1-1 was shown to be a weak allele mutant and a new ATML1 null mutation, caused by a T-DNA insertion in the homeobox, combined with a PDF2 mutation turned out to cause developmental arrest at the globular stage. Transcript levels of some epidermal genes were reduced in the atml1-1 pdf2-1 mutant background, suggesting that ATML1 and PDF2 are required for epidermal differentiation. PROTODERMAL FACTOR2 ( PDF2), an ATML1 paralog expressed in the epidermis, functions redundantly with ATML1 the atml1-1 pdf2-1 double mutant is seedling-lethal harboring reduced cotyledons and narrow leaves lacking an epidermis. The atml1-1 single mutant, which has a T-DNA insertion near the 3′ end of the ORF, did not show a clear abnormality. Recently, we reported that although ATML1 was strongly expressed in the outermost cells, weak expression was also detected in the inner cells of the embryos, especially in the subepidermal cells ( Figure 2a).ĪTML1 loss-of-function mutant phenotypes were first described in 2003 and its role in plant development was explored. Furthermore, when the reporter was fused with a destruction-box motif, which degrades the reporter protein at anaphase and enables detection of only newly synthesized protein after cell division, ATML1 promoter activity was hardly detected in the inner cells of the 16-cell stage embryos, suggesting that ATML1 transcription is restricted to the outermost cells from the 16-cell stage. ![]() Detailed expression analysis in the embryos, with the aid of a sensitive reporter gene, revealed that ATML1 promoter was also active in the basal cell of the one-cell stage embryo and in the suspensor cells ( Figure 2a). ATML1 promoter activity was also detected in the outermost cells of the root meristem ( Figure 2c). Īfter the first report, ATML1 expression pattern has been re-examined in more details by several researchers. Observed increase in cytokinin, a plant hormone that promotes cell proliferation, in VLCFA-deficient seedlings suggests that VLCFAs or their derivatives play a role in repressing cytokinin biosynthesis in the vasculature. ![]() ![]() It has also been reported that production of very-long-chain fatty acids (VLCFAs) in the epidermis, which are components of the cuticle wax, is required for repressing cell proliferation in the vascular tissue. These observations suggest that the epidermal layer restricts the extent of shoot growth depending on the activity of BR signaling. Activation of BR signaling in the outermost layer of those mutants rescued their dwarf phenotypes, whereas inactivation of BR signaling in the wild-type epidermal layer made plants small. Brassinosteroid (BR) is a plant hormone promoting cell division and expansion and the BR response and biosynthetic mutants show a severe dwarf phenotype. In addition to its protective functions, the epidermis plays an important role in controlling plant growth.
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