A Repressor Protein Complex Regulates Leaf Growth in Arabidopsis

Abstract

Cell number is an important determinant of final organ size. In the leaf, a large proportion of cells are derived from the stomatal lineage. Meristemoids, which are stem cell-like precursor cells, undergo asymmetric divisions, generating several pavement cells adjacent to the two guard cells. However, the mechanism controlling the asymmetric divisions of these stem cells prior to differentiation is not well understood. Here, we characterized PEAPOD (PPD) proteins, the only transcriptional regulators known to negatively regulate meristemoid division. PPD proteins interact with KIX8 and KIX9, which act as adaptor proteins for the corepressor TOPLESS. D3-type cyclin encoding genes were identified among direct targets of PPD2, being negatively regulated by PPDs and KIX8/9. Accordingly, kix8 kix9 mutants phenocopied PPD loss-of-function producing larger leaves resulting from increased meristemoid amplifying divisions. The identified conserved complex might be specific for leaf growth in the second dimension, since it is not present in Poaceae (grasses), which also lack the developmental program it controls.

Increasing seed size and quality by manipulating BIG SEEDS1 in legume species

“…PPD1 and PPD2, two tandemly duplicated BS1 orthologs in Arabidopsis, regulate the size and shape of leaves and siliques, but not seeds, by repressing the secondary cell proliferation, asymmetric division of meristemoids (20,21). In ppd1 ppd2 deletion and knock-down mutants, asymmetric cell division and the number of small cells are increased in leaves (20,21), leading to a substantially altered epidermal cell pattern and a significantly reduced stomatal index.…”

“…In ppd1 ppd2 deletion and knock-down mutants, asymmetric cell division and the number of small cells are increased in leaves (20,21), leading to a substantially altered epidermal cell pattern and a significantly reduced stomatal index. This result is in contrast to the phenotype seen in the mtbs1-1 mutants in which only cell number, but not cell size and pattern and stomatal index, is changed.…”

“…It is related to two tandemly repeated genes in Arabidopsis, At4g14713 (PEAPOD1 or PPD1) and At4g14720 (PPD2), that have been shown to regulate the size and shape of leaves and siliques but not seeds (20,21). Protein subcellular localization showed that BS1-GFP fusion proteins were localized to the nucleus (Fig.…”

“…Arabidopsis PPD1 and PPD2, the BS1 orthologs, repress meristemoid cell division in leaves (20,21)). In loss-of-function and knock-down ppd mutants, numerous small cells that surround stomata were generated, giving rise to enlarged and dome-shaped leaves (20-22) (SI Appendix, Fig.…”

From network to phenotype: the dynamic wiring of an Arabidopsis transcriptional network induced by osmotic stress

“…After a few days, cells at the distal end of the leaf exit the mitotic cell cycle and start to expand and subsequently differentiate (Donnelly et al , 1999; Andriankaja et al , 2012). At this point, growth is merely driven by cell expansion and, in the epidermis, by the division activity of meristemoid cells (White, 2006; Andriankaja et al , 2012; Gonzalez et al , 2015). Both cell proliferation and cell expansion can be adversely affected by mild osmotic stress conditions (Skirycz et al , 2011; Huber et al , 2014).…”