PACLOBUTRAZOL-RESISTANCE Gene Family Regulates Floral Organ Growth with Unequal Genetic Redundancy in Arabidopsis thaliana

A ( ) gene family, consisting of six genes in , encodes a group of helix-loop-helix proteins that act in the growth-promoting transcriptional network. To delineate the specific role of each of the genes in organ growth, we took a reverse genetic approach by constructing high order loss-of-function mutants of . In addition to dwarf vegetative growth, some double or high order mutants exhibited defective floral development, resulting in reduced fertility. While is normally fertile, both and showed reduced fertility. Further, the reduced fertility was exacerbated in the mutant, indicative of the redundant and critical roles of these PREs. Self-pollination assay and scanning electron microscopy analysis showed that the sterility of was mainly ascribed to the reduced cell elongation of anther filament, limiting access of pollens to stigma. We found that the expression of a subset of flower-development related genes including , , and was downregulated in the flowers. Given these results, we propose that PREs, with unequal functional redundancy, take part in the coordinated growth of floral organs, contributing to successful autogamous reproduction in