MYB and HD-ZIP IV homologs related to trichome formation are involved in epidermal bladder cell development in the halophyte Mesembryanthemum crystallinum L.

• Main Authors: Siranet Roeurn, Narihiro Hoshino, Ken-taro Soejima, Yuuka Inoue, John C. Cushman, Sakae Agarie
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2017-01-01
• Series: Plant Production Science
• Subjects: Cotton fiber; epidermal bladder cells; gene expression; Mesembryanthemum crystallinum; mutant; transgenic plant
• Online Access: http://dx.doi.org/10.1080/1343943X.2017.1279528
• ISSN: 1343-943X; 1349-1008

The common ice plant, Mesembryanthemum crystallinum L., a halophytic new functional leafy vegetable crop, develops epidermal bladder cells (EBCs) on the surfaces of its aerial organs. Our previous studies of the physiological characteristics of the wild-type and the EBC-less mutant indicated that EBCs sequester salt and maintain ion homeostasis within photosynthetically active tissues. The EBC has been thought to be a modified trichome; however, molecular mechanisms governing EBC development in the common ice plant have not been fully understood. Here, we have analyzed the steady-state mRNA abundance of nineteen cotton fiber-related gene homologs and eight Arabidopsis trichome development-related genes, and found that a MYB transcription factor homolog (McMYB2) and a GLABRA2-like gene (McC4HDZ) were preferentially expressed in wild-type plants, whereas a putative TRIPTYCHON (McTRY)- and CAPRICE-like gene (McCPC) were preferentially expressed in the EBC-mutant. The full-length cDNA sequences of these homologs were determined, and constructs containing McC4HDZ and McMYB2 were introduced into an Arabidopsis trichome-less mutant and wild-type plants. Overexpression of McMYB2 in wild-type Arabidopsis increased trichome number, associated with activation of the trichome development-related gene, GLABRA2 (GL2). Moreover, overexpression of McC4HDZ partially complemented trichome development in the trichome-less mutant of gl2-1, and resulted in increased trichome number in wild-type Arabidopsis, associated with the upregulation of key trichome-positive regulators GLABRA1 (GL1) and TRANSPARENT TESTA GLABRA1 (TTG1). These results suggest that McMYB2 and McC4HDZ could be functional in Arabidopsis trichome formation, implying that EBCs of the common ice plant and trichomes of Arabidopsis may share some molecular mechanisms in their development.