Analysis on the Regulation of Cell Number and Cell Size by Heteroblasty

Abstract

We isolated four arabidopsis mutants that showed increased cell number and decreased cell size in leaves. Three of them showed accelerated heteroblasty. In Arabidopsis thaliana, adult leaves have more and smaller cells than juvenile leaves. Therefore, leaves of these three mutants might have characteristics of adult leaves of wild type (Usami et al., 2007 Annual meeting of JSPP).
In the present study, we focused on the role of miR156 mediated regulation of SPL transcription factors in heteroblastic changes of cell number and size. One of the three accelerated heteroblasty mutants we isolated had a mutation in miR156 target site of SPL15 gene and showed elevated SPL15 mRNA level. And in miR156 constitutively expressing plants, number and size of leaf cells did not differ significantly between higher and lower nodes. These results indicate that SPL transcription factors might be involved in cell number and size regulation in leaves.