Two New Male-Sterile Mutants of Zea mays (Poaceae) with Abnormal Tapetal Cell Morphology

Abstract

Two new recessive male‐sterile mutants of Zea mays (Poaceae), or maize, were studied to identify the timing of pollen abortion and to examine the involvement of anther wall cell layers. The results of test crosses indicated that these mutants were not allelic with any known male‐sterile mutants of maize. Light and transmission electron microscopy were used to compare pollen development in homozygous male‐sterile mutants to that in fertile heterozygous siblings. In both mutants, microspores abort soon after release from the meiotic tetrad. However, the two mutations have strikingly different phenotypes. Large lipid bodies accumulate in the tapetal cells as the microspores vacuolate and die in the mutant ms25. Large vacuoles appear in both the tapetal cells and the young microspores as they begin to disintegrate in the mutant ms26. Because abnormal tapetal cell morphology is detected in both mutants, it is possible that both of these mutations affect the expression of genes in tapetal cells.

Comparative microsporangium development in male‐fertile and male‐sterile flowers ofConsolea(Cactaceae): When and how does pollen abortion occur

“…Tapetum abnormalities like hypertrophied and highly vacuolated cells, have been observed in the three types of male sterility: CMS (Overman & Warmke, 1972;Polowick & Sawhney, 1990;Worral et al 1992;Hidalgo et al 1999); GMS (Rick 1948;Childers, 1952;Kaul & Singh, 1966;Graybosch & Palmer, 1985;Loukides et al 1995;Hernould et al 1998;Engelke et al 2002;Smith et al 2002), and GCMS (Brooks et al 1966;Colhoun & Steer, 1981). Some of the morphological features that Consolea aborting anthers exhibit are comparable to features of both CMS and GMS systems.…”

“…Recently, emphasis has shifted towards the understanding of stamen and male gametophyte development, and the genes involved in those processes in Arabidopsis thaliana (Chaudhury et al 1994;Sanders et al 1999;Zhang et al 2002). In order to determine the timing and place of the male sterility process, anatomical studies were first performed at the light microscope level (Singh & Rhodes, 1961;Dubey & Singh, 1965;Brooks et al 1966;Joppa et al 1966;Kaul & Singh, 1966;Chauhan & Singh, 1966;Pritchard & Hutton, 1972;Graybosch et al 1984;Yonggen & Rutger, 1984;Sawhney & Bhadula, 1988;Kini et al 1994) and later at the ultrastructural level (Overman & Warmke, 1972;Warmke & Lee, 1977;Horner, 1977;Lee et al , 1980Pollak, 1992;Loukides et al 1995). Recent studies combined inheritance, molecular, and ultrastructure techniques for a more comprehensive analysis of male sterility (Dawson et al 1992;Chaudhury et al 1994;Jin et al 1997;Sanders et al 1999).…”

Maize Tapetum Xylanase Is Synthesized as a Precursor, Processed and Activated by a Serine Protease, and Deposited on the Pollen

“…This website program indicates a possibility that the protein is targeted to the peroxisomes because of the presence the tripeptide AKL in the 60-kDa pre-xylanase and the 35-kDa xylanase. We discount this possibility, because the tripeptide AKL, unlike those in peroxisomal proteins, is not present at or very near the C terminus, and because we (data not shown), as well as others (13,14), did not observe apparent peroxisomes in the tapetum cells. We subfractionated the extract of stage-3 anthers by differential centrifugation after the microspores (and the attached 35-kDa xylanase) in the extract had been removed by a short and low speed centrifugation.…”

“…The coat also contains minor proteins involved in self-incompatibility that are synthesized in the pollen interior (11,12). In wind-pollinating species, the pollen coat is thin (13,14), and major biochemical studies have been carried out only with maize (15). The coat of maize pollen contains undefined neutral lipids and a predominant protein.…”

Significance of Unusual Features of the Anthers of Spathoglottis plicata Bl.

“…During the period of callose deposition and meiosis, the wall fibrils loosen and become fibrous (Polowick and Sawhney 1993). Thus, by virtue of its extremely thin cell walls, tapetum functions as a secretory and nutritive tissue and regulates the supply of assimilate into the anther locule (Bedinger 1992, Loukides et al 1995. Therefore, it is natural to assume that thick cell walls of meiocytes and tapetum might inhibit the transport of assimilates into the anther locule.…”