Identification of PAN2 by quantitative proteomics as a leucine-rich repeat-receptor-like kinase acting upstream of PAN1 to polarize cell division in maize.

Mechanisms governing the polarization of plant cell division are poorly understood. Previously, we identified pangloss1 (PAN1) as a leucine-rich repeat-receptor-like kinase (LRR-RLK) that promotes the polarization of subsidiary mother cell (SMC) divisions toward the adjacent guard mother cell (GMC) during stomatal development in maize (Zea mays). Here, we identify pangloss2 (PAN2) as a second LRR-RLK promoting SMC polarization.

ROP GTPases act with the receptor-like protein PAN1 to polarize asymmetric cell division in maize.

Plant Rho family GTPases (ROPs) have been investigated primarily for their functions in polarized cell growth. We previously showed that the maize (Zea mays) Leu-rich repeat receptor-like protein PANGLOSS1 (PAN1) promotes the polarization of asymmetric subsidiary mother cell (SMC) divisions during stomatal development. Here, we show that maize Type I ROPs 2 and 9 function together with PAN1 in this process.

Determination of symmetric and asymmetric division planes in plant cells.

The cellular organization of plant tissues is determined by patterns of cell division and growth coupled with cellular differentiation. Cells proliferate mainly via symmetric division, whereas asymmetric divisions are associated with initiation of new developmental patterns and cell types. Division planes in both symmetrically and asymmetrically dividing cells are established through the action of a cortical preprophase band (PPB) of cytoskeletal filaments, which is disassembled upon transition to metaphase, leaving behind a cortical division site (CDS) to which the cytokinetic phragmoplast is later guided to position the cell plate.

PAN1: a receptor-like protein that promotes polarization of an asymmetric cell division in maize.

Polarization of cell division is essential for eukaryotic development, but little is known about how this is accomplished in plants. The formation of stomatal complexes in maize involves the polarization of asymmetric subsidiary mother cell (SMC) divisions toward the adjacent guard mother cell (GMC), apparently under the influence of a GMC-derived signal. We found that the maize pan1 gene promotes the premitotic polarization of SMCs and encodes a leucine-rich repeat receptor-like protein that becomes localized in SMCs at sites of GMC contact.

Two WD-repeat genes from cotton are functional homologues of the Arabidopsis thaliana TRANSPARENT TESTA GLABRA1 (TTG1) gene.

Cotton fibres are single, highly elongated cells derived from the outer epidermis of ovules, and are developmentally similar to the trichomes of Arabidopsis thaliana. To identify genes involved in the molecular control of cotton fibre initiation, we isolated four putative homologues of the Arabidopsis trichome-associated gene TRANSPARENT TESTA GLABRA1 (TTG1). All four WD-repeat genes are derived from the ancestral D diploid genome of tetraploid cotton and are expressed in many tissues throughout the plant, including ovules and growing fibres.