Activation of miR165b represses AtHB15 expression and induces pith secondary wall development in Arabidopsis. (24th June 2015)

• Record Type: Journal Article
• Authors: Du, Qian; Avci, Utku; Li, Shengben; Gallego‐Giraldo, Lina; Pattathil, Sivakumar; Qi, Liying; Hahn, Michael G.; Wang, Huanzhong
• Is Part Of: Plant journal. Volume 83:Number 3(2015:Aug.)
• Page Start: 388
• Page End: 400
• Publication Date: 2015-06-24
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12897
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12897-abs-0001"> <title>Summary</title> <p>Secondary cell‐wall thickening takes place in sclerenchyma cells, but not in surrounding parenchyma cells. The molecular mechanism of switching on and off secondary wall synthesis in various cell types is still elusive. Here, we report the identification of a dominant mutant <italic>stp–2d</italic> showing secondary wall thickening in pith cells (STP). Immunohistochemistry assays confirmed accumulation of secondary cell walls in the pith cells of the <italic>stp–2d</italic> mutant. Activation of microRNA 165b (<italic>miR165b</italic>) expression is responsible for the STP phenotype, as demonstrated by transgenic over‐expression experiments. The expression of three class III HD–ZIP transcription factor genes, including <italic>AtHB15</italic>, was repressed in the <italic>stp–2d</italic> mutant. Transgenic over‐expression of a mutant form of <italic>AtHB15</italic> that is resistant to <italic>miR165</italic>‐mediated cleavage reversed the <italic>stp–2d</italic> mutant phenotype to wild‐type, indicating that AtHB15 represses secondary wall development in pith. Characterization of two <italic>athb15</italic> mutant alleles further confirmed that functional AtHB15 is necessary for retaining primary walls in parenchyma pith cells. Expression analyses of cell‐wall synthetic genes and wall‐related transcription factors indicated that a transcriptional pathway is involved in AtHB15 function. These results provide insight into the molecular mechanism of secondary cell‐wall development.</p> </abstract>