UC San Diego

Asymmetric cell division is a vital component of plant development. It enables cell differentiation and cell diversity. A key component of asymmetric cell division is cell signaling. Signals are believed to control polarization and orientation of asymmetric divisions during stomatal development. The findings of this report suggest that PNL1 and PNL2, two LRR-RLKs found in Arabidopsis and closely related to maize PAN1 LRR-RLK, are possibly involved in the signaling events occurring during the asymmetric divisions involved in stomatal complex formation. Upon disruption of normal PNL1 and PNL2 protein synthesis via insertion mutations, an apparent double stomata phenotype was observed characterized by two stomates developing in direct contact and thus violating the one-cell-spacing rule. The frequency of the double stomata was similar in both single and double mutants suggesting that PNL1 and PNL2 may function as a heterodimer. Despite observing a low frequency of double stomata, the mutant phenotype was observed in both pnl1and pnl2 mutants and not in Columbia wild type. Consistent with the mutant phenotype, YFP tagging of the PNL2 protein revealed expression in developing stomata of young leaf primordia. PNL2 expression was observed in recently divided meristemoid cells, their neighboring sister cells and to a lesser extent in older sisters of the cell pair. These findings suggest that PNL2 may function as a plasma membrane localized inhibitory receptor that prevents stomata from forming adjacent to each other, yet more extensive research is necessary to acquire further knowledge as to how PNL1 and PNL2 may function in developing stomata