May play a role in leaf development. Required for leaf mesophyll cell division in the early stages of leaf organogenesis (PubMed:12848826, PubMed:16873448). Acts in a developmental pathway that involves PPT1/CUE1 but does not include ASE2/DOV1 (PubMed:16873448). Highly expressed in the vasculature of developing leaf primordia, margins of fully expanded leaves, hydathodes of rosette of cauline leaves, basal region of the lamina, stipules, root tips, stamens and in the abscission zone of the funiculus. During embryo development, expressed from torpedo stage onwards. Pale interveinal phenotype due to marked reduction in the density of mesophyll cells in interveinal regions of leaves (PubMed:12848826, PubMed:16873448). Increased sensitivity to ozone and a virulent strain of the bacterial pathogen Pseudomonas syringae pv. maculicola (PubMed:12848826). Belongs to the RETICULATA family.