Abstract
A PACLOBUTRAZOL-RESISTANCE (PRE) gene family, consisting of six genes in Arabidopsis thaliana, 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 PRE genes in organ growth, we took a reverse genetic approach by constructing high order pre loss-of-function mutants of Arabidopsis thaliana. In addition to dwarf vegetative growth, some double or high order pre mutants exhibited defective floral development, resulting in reduced fertility. While pre2pre5 is normally fertile, both pre2pre6 and pre5pre6 showed reduced fertility. Further, the reduced fertility was exacerbated in the pre2pre5pre6 mutant, indicative of the redundant and critical roles of these PREs. Self-pollination assay and scanning electron microscopy analysis showed that the sterility of pre2pre5pre6 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 ARGOS, IAA19, ACS8, and MYB24 was downregulated in the pre2pre5pre6 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 Arabidopsis thaliana.
Highlights
Coordinated organ growth is essential for the determination of organ architecture and its biological functions
By comparing phenotypes of different combinations of high order pre mutants, we suggest that PRE gene family members take part, in an unequally redundant manner, in the regulation of cell elongation/expansion for diverse aspects of growth and development
Sci. 2019, 20, 869 members, we found that all of the PRE members in Arabidopsis thaliana could interact with PAR1 or PAR2, a class of PRE-interacting HLH proteins [29], in yeast two-hybrid assay (Figure S1)
Summary
Coordinated organ growth is essential for the determination of organ architecture and its biological functions. The coordinated growth of anther filament and style, as well as the release of functional pollens, is essential. The stamen development is controlled by multiple phytohormones including GA, BLs, auxins, and JA [4,5,6,7]. Deficiency of those hormones causes male sterility [4,6,8,9,10,11,12,13,14]. The expression of MYB21/MYB24 is regulated by multiple plant growth hormones including GA, JA, and auxin in part with a hierarchical relationship. GA and ARF6/ARF8 regulate JA-biosynthetic genes to regulate the production of JA, which in turn activates the expression of MYB21/MYB24 [15,16]
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