The MADS Box Transcription Factor ZmMADS2 Is Required for Anther and Pollen Maturation in Maize and Accumulates in Apoptotic Bodies during Anther Dehiscence

Abstract

The maize (Zea mays) late pollen gene ZmMADS2 belongs to the MIKC type of MADS box transcription factor genes. Here, we report that ZmMADS2, which forms a homodimer in yeast (Saccharomyces cerevisiae), is required for anther dehiscence and pollen maturation. Development of anthers and pollen was arrested at 1 d before dehiscence in transgenic plants expressing the ZmMADS2-cDNA in antisense orientation. Temporal and spatial expression analyses showed high amounts of ZmMADS2 transcripts in endothecium and connective tissues of the anther at 1 d before dehiscence and in mature pollen after dehiscence. Transient transformation of maize and tobacco (Nicotiana tabacum) pollen with the luciferase reporter gene under the control of different ZmMADS2 promoter deletion constructs demonstrated the functionality and tissue specificity of the promoter. Transgenic maize plants expressing a ZmMADS2-green fluorescent protein fusion protein under control of the ZmMADS2 promoter were used to monitor protein localization during anther maturation and pollen tube growth. High amounts of the fusion protein accumulate in degenerating nuclei of endothecial and connective cells of the anther. A possible function of ZmMADS2 during anther dehiscence and pollen maturation and during pollen tube growth is discussed.In higher plants, development of the haploid male gametophyte (pollen) is closely related to maturation of the surrounding sporophytic tissues of the anther. In angiosperms, anther tissues arise from three "germ" layers, designated L1 to L3 (Satina and Blakeslee, 1941). In maize (Zea mays), tapetal initials and pollen mother cells are generated by the division of a diploid sporophytic cell. The tapetal initial cells give rise to the outer, middle, and inner (tapetal) layers of the sporangium wall (Kiesselbach, 1999). The sporogenous cells (pollen mother cells) undergo meiosis, giving rise to a tetrad of haploid cells, which are released as free microspores (McCormick, 1993). During microgametogenesis, microspores develop into mature pollen by two mitotic divisions. The first mitotic division results in a vegetative and a generative cell. The latter divides either in the pollen grain or the pollen tube to generate the two haploid sperm cells. In maize, the generative cell within the young pollen divides before maturation of the anther is completed to generate a tricellular mature pollen grain (Bedinger, 1992).During gametogenesis, the innermost cell layer of the anther, the tapetum, plays a crucial role for the release and nutrition of the microspores. Microspores are supplied with nutrients from the tapetum; therefore, mutations affecting tapetal development lead to abortion of microgametogenesis and male sterility (Cheng et al., 1979; Chaudhury, 1993;Okada et al., 1999;Wilson et al., 2001;Kapoor et al., 2002). Tapetal cells secrete callase to release the meiotic tetrad from an enclosing callose wall. The exact timing and proper function of callase has been shown to be essential for pollen development. Precursors for the biosynth...

Rice MADS3 Regulates ROS Homeostasis during Late Anther Development

“…Other MADS box genes, such as SPOROCYTELESS/NOZZLE (SPL/NZZ) (Yang et al, 1999;Schiefthaler et al, 1999) and AG (Ito et al, 2004(Ito et al, , 2007 from Arabidopsis and MADS2 from maize (Zea mays; Schreiber et al, 2004), have been implicated in regulating anther development. SPL/NZZ regulates the formation of anther walls and pollen mother cells, as the primary sporogenous cells cannot form pollen mother cells in spl anthers, thereby blocking early cell differentiation (Yang et al, 1999).…”

“…During later developmental stages, AG continues its expression in the anther and regulates anther dehiscence by directly regulating the expression of the gene that encodes a jasmonic acid (JA) synthetic enzyme, DEFECTIVE IN ANTHER DEHISCENCE1 (Ito et al, 2007). Maize MADS2 is required for anther dehiscence and pollen maturation, and knockdown of MADS2 resulted in abortion of anthers and defective pollen development (Schreiber et al, 2004).…”

Isolation and characterization of the papaya MADS-box E-class genes, CpMADS1 and CpMADS3, and a TM6 lineage gene CpMADS2

“…With the progress in understanding of the control of MADS-box genes in organ differentiation of flowers in Arabidopsis, studies have been conducted to elucidate the relationship between the MADS-box genes and sex determination in economic crops with gender specificity, such as monoecious cucumber (Kater et al, 2001) and corn (Heuer et al, 2001;Schreiber et al, 2004), dioecious asparagus (Park et al, 2003), and trioecious papaya (Ackerman et al, 2008). Trioecious papaya is an economically important sub-tropical fruit crop, with its regular hermaphroditic flowers and production yield is emphasized in hermaphrodite papaya cultivation (Arkle Jr. and Nakasone, .…”

The pollen-specific DEFH125 promoter from Antirrhinum is bound in vivo by the MADS-box proteins DEFICIENS and GLOBOSA

“…The putative ATG start codon is indicated by a black box a DEFH125 homolog from Zea mays, is also expressed in pollen and pollen tube but has evolved an additional function. ZmMADS2 expression is also transiently detectable in the endothecium and connective tissues of the anther (Schreiber et al 2004). Functional analysis showed that this gene not only plays a role in pollen maturation but is also involved in anther dehiscence (Schreiber et al 2004).…”