AINTEGUMENTA-LIKE genes have partly overlapping functions with AINTEGUMENTA but make distinct contributions to Arabidopsis thaliana flower development.

Beth A Krizek

doi:10.1093/jxb/erv224

Abstract

AINTEGUMENTA (ANT) is an important regulator of Arabidopsis flower development that has overlapping functions with the related AINTEGUMENTA-LIKE6 (AIL6) gene in floral organ initiation, identity specification, growth, and patterning. Two other AINTEGUMENTA-LIKE (AIL) genes, AIL5 and AIL7, are expressed in developing flowers in spatial domains that partly overlap with those of ANT. Here, it is shown that AIL5 and AIL7 also act in a partially redundant manner with ANT. The results demonstrate that AIL genes exhibit unequal genetic redundancy with roles for AIL5, AIL6, and AIL7 only revealed in the absence of ANT function. ant ail5 and ant ail7 double mutant flowers show alterations in floral organ positioning and growth, sepal fusion, and reductions in petal number. In ant ail5, petals are often replaced by filaments or dramatically reduced in size. ant ail7 double mutants produce increased numbers of carpels, which have defects in valve fusion and a loss of apical tissues. The distinct phenotypes of ant ail5, ant ail7 and the previously characterized ant ail6 indicate that AIL5, AIL6, and AIL7 make unique contributions to flower development. These distinct roles are also supported by genetic analyses of ant ail triple mutants. While ant ail5 ail6 triple mutants closely resemble ant ail6 double mutants, ant ail5 ail7 triple mutants exhibit more severe deviations from the wild type than either ant ail5 or ant ail7 double mutants. Furthermore, it is shown that AIL5, AIL6, and AIL7 act in a dose dependent manners in ant and other mutant backgrounds.

Highlights

Flowers arise on the flanks of the inflorescence meristem at the sites of auxin maxima (Reinhardt et al, 2003)
The results demonstrate that AIL genes exhibit unequal genetic redundancy with roles for AIL5, AIL6, and AIL7 only revealed in the absence of ANT function. ant ail5 and ant ail7 double mutant flowers show alterations in floral organ positioning and growth, sepal fusion, and reductions in petal number
Genotyping of ail5-2, ail5-3, ail6-2, and ail7-1 was performed using the primers listed in Supplementary Table S1 at JXB online

Summary

Introduction

Flowers arise on the flanks of the inflorescence meristem at the sites of auxin maxima (Reinhardt et al, 2003). The sites of floral organ initiation within a flower appear to correspond to auxin maxima, it is not clear if auxin specifies the founder cell population or accumulates after these cells are specified and promotes organ outgrowth (Chandler et al, 2011). After initiation, these primordia adopt a sepal, petal, stamen or carpel fate as a consequence of the activities of distinct combinations of four classes of floral organ identity genes (reviewed in Krizek and Fletcher, 2005). These MADS domain protein complexes appear to act throughout floral organ development activating both early and later targets during floral organogenesis (Ito et al, 2004, 2007; Kaufmann et al, 2010; Wuest et al, 2012; O’Maoleidigh et al, 2013)

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