TheSPOROCYTELESS/NOZZLEGene Is Involved in Controlling Stamen Identity in Arabidopsis

Xiaodong Liu,Gengxiang Jia,Brandon Seubert,Toshiro Ito,Sriram Parameswaran,Max Auer,Heather A Owen,Dazhong Zhao,Jian Huang,Amy Rymaszewski

doi:10.1104/pp.109.145896

Abstract

The stamen, which consists of an anther and a filament, is the male reproductive organ in a flower. The specification of stamen identity in Arabidopsis (Arabidopsis thaliana) is controlled by a combination of the B genes APETALA3 (AP3) and PISTILLATA, the C gene AGAMOUS (AG), and the E genes SEPALLATA1 (SEP1) to SEP4. The "floral organ-building" gene SPOROCYTELESS/NOZZLE (SPL/NZZ) plays a central role in regulating anther cell differentiation. However, much less is known about how "floral organ identity" and floral organ-building genes interact to control floral organ development. In this study, we report that ectopic expression of SPL/NZZ not only affects flower development in the wild-type background but also leads to the transformation of petal-like organs into stamen-like organs in flowers of ap2-1, a weak ap2 mutant allele. Moreover, our loss-of-function analysis indicates that the spl/nzz mutant enhances the phenotype of the ag weak allele ag-4. Furthermore, ectopic expression and overexpression of SPL/NZZ altered expression of AG, SEP3, and AP2 in rosette leaves and flowers, while ectopic expression of SPL/NZZ resulted in ectopic expression of AG and SEP3 in the outer whorls of flowers. Our results indicate that the SPL/NZZ gene is engaged in controlling stamen identity via interacting with genes required for stamen identity in Arabidopsis.

Highlights

The stamen, which consists of an anther and a filament, is the male reproductive organ in a flower
The SPOROCYTELESS/ NOZZLE (SPL/NZZ) gene is critical for anther morphogenesis, since spl/nzz mutant plants fail to produce the main structures of the anther, including microsporocytes and anther walls (Schiefthaler et al, 1999; Yang et al, 1999)
Interactions between “stamen identity” and “stamen-building” genes have not been extensively studied in the context of development, excellent advances have been made in understanding stamen identity, early anther cell differentiation, male meiosis, pollen development, and anther dehiscence (Goldberg et al, 1993; Walbot and Evans, 2003; Jack, 2004; McCormick, 2004; Scott et al, 2004; Ma, 2005; Feng and Dickinson, 2007; Borg et al, 2009; Wilson and Zhang, 2009; Zhao, 2009)

Summary

Introduction

The stamen, which consists of an anther and a filament, is the male reproductive organ in a flower. The “floral organ-building” gene SPOROCYTELESS/ NOZZLE (SPL/NZZ) plays a central role in regulating anther cell differentiation. After the specification of stamen identity, anther development involves a series of cell division, cell differentiation, and cell death, resulting in the formation of reproductive microsporocytes and somatic cell layers. Besides genes that encode signaling proteins (Canales et al, 2002; Zhao et al, 2002; Yang et al, 2003; Albrecht et al, 2005; Colcombet et al, 2005; Hord et al, 2006; Mizuno et al, 2007; Jia et al, 2008; Zhao, 2009), the SPOROCYTELESS/NOZZLE (SPL/NZZ) gene plays a central role in controlling early anther cell differentiation (Schiefthaler et al, 1999; Yang et al, 1999). We hypothesize that SPL/NZZ might be involved in controlling stamen identity

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