Abnormal Vacuolization of the Tapetum During the Tetrad Stage is Associated with Male Sterility in the Recessive Genic Male Sterile <Emphasis Type="Italic">Brassica napus</Emphasis> L. Line 9012A

In the recessive genic male sterile line 9012A of Brassica napus, pollen development is affected during the tetrad stage. According to the light and electron microscopy analysis of tapetal cells and tetrads, the sterile tapetal cells swelled with expanded vacuoles at the early tetrad stage and finally filled the center of the locules where a majority of tetrads encased with the thick callose wall collapsed and degraded. We suggested that an absence of callase, which is a wall-degrading enzyme stored in the vacuoles of tapetal cells before secretion, resulted in the failure of tetrad separation. Moreover, transmission electron microscopy analysis showed that the secretory tapetal cells were not observed in sterile anthers, which indicated that the transition of the tapetum from the parietal type to the secretory type was probably aberrant. In plants, degeneration of the tapetum is thought to be the result of programmed cell death (PCD). PCD of tapetal cells was investigated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and signals indicative of deoxyribonucleic acid fragmentation were detected much earlier in sterile anther than in fertile anther. This suggests that tapetal breakdown does not occur by the normal procession of PCD and might be following an alternative mechanism of unscheduled apoptosis in line 9012A. This research supports the hypothesis that premature PCD is associated with male sterility in B. napus.     

An ultrastructural,cytochemical and immunofluorescence study of postmeiotic development of plasmodial tapetum inTradescantia virginiana L. and its relevance to the pathway of sporopollenin secretion

Summary Establishment of a tapetal plasmodium in postmeiotic stages in anther locules ofTradescantia virginiana encloses the tetrads in membrane-limited compartments. The perispore membrane (PSM), around each tetrad, is derived from composite tapetal cell plasma membranes. The tapetum acquires an abundance of ER and ribosomes and by the late tetrad stage the PSM and its underlying cytoplasm exhibit specialized features, studied here by ZnIO impregnation, osmium maceration, application of indirect immunofluorescence employing antitubulin, conventional thin sectioning and the Thiéry reaction. These features include: labyrinthine convolutions of the PSM resulting from migration of membranous sacs and their partial fusion to the PSM, an intimate relationship of tubular ER with the convoluted PSM, and microtubules underlying the PSM and among the membranous sacs. At the same time membrane-bound granules, comparable to but smaller and simpler than tapetal orbicules of secretory tapeta, form in the convolutions. It is postulated that the ER supplies precursors of sporopollenincontaining parts of the spore wall, that the PSM-associated microtubules stabilise the whole secretory apparatus at the tapetum-spore interface, and that the precursors are expelled into the lumen bounded by the PSM and then accreted upon the orbicule-like granules or the developing spore wall. With dissolution of the callosic wall, the plasmodium invades the intermicrosporal spaces of late tetrads, the PSM unfolding its elaborations and becoming closely appressed to the exinous surfaces of individual spores. Microtubules, although present during this phase of invasion, do not seem to propel the invasion processes and may have roles in shape maintenance. During pollen mitosis and enlargement the tapetal cytoplasm accumulates lipidic globules. A late phase of Golgi activity precedes accumulation of vesicles or vacuoles near the spores, these being bounded by single or multiple tripartite membranes. With anther desiccation, portions of plasmodium are deposited on the pollen surface in the form of tryphine, the deposits containing stacked membrane-like bilayers.     

THE CYTOLOGY OF POLLEN ABORTION IN C-CYTOPLASMIC MALE-STERILE CORN ANTHERS

Anther development of the C-cytoplasmic male-sterile (cms C) and the normal cytoplasm version (N) in the W182BN corn inbred was studied by light and electron microscopy. Deviation from normal pollen development was first observed in the tapetal cells at the tetrad stage of development. Two types of tapetal abnormalities were observed in plants with C cytoplasm. The first behaved like the N anther until the tetrad stage, when numerous small vacuoles appeared in the tapetal cells. Inner and radial tapetal cell walls broke down normally, but irregular Ubisch body deposition was observed, and exine development was inhibited and delayed. The tapetum and microspores disintegrated at the intermediate microspore stage. The second type of tapetum was highly vacuolated at the early tetrad stage, with dense inner and radial cell walls that remained intact and enlarged when the tetrads aborted. No organellar abnormalities, such as the mitochondrial changes observed in cms T, were observed in C anthers.     

Ultrastructure of microsporogenesis and microgametogenesis inArabidopsis thaliana (L.) Heynh. ecotype Wassilewskija (Brassicaceae)

Summary The process of microsporogenesis and microgametogenesis was studied at the ultrastructural level in wild-typeArabidopsis thaliana ecotype Wassilewskija to provide a basis for comparison with nuclear male-sterile mutants of the same ecotype. From the earliest stage studied to mature pollen just prior to anther dehiscence, microsporocyte/microspore/pollen development follows the general pattern seen in most angiosperms. The tapetum is of the secretory type with loss of the tapetal cell walls beginning at about the time of microsporocyte meiosis. Wall loss exhibits polarity with the tapetal protoplasts becoming located at a distance from the inner tangential walls first, followed by an increase in distance from the radial walls beginning at the interior edge and progressing outward. The inner tangential and radial tapetal walls are completely degenerated by the microspore tetrad stage. Unlike other members of the Brassicaceae that have been studied, the tapetal cells ofA. thaliana Wassilewskija also lose their outer tangential walls, and secretion occurs from all sides of the cells. Exine wall precursors are secreted from the tapetal cells in a process that appears to involve dilation of individual endoplasmic reticulum cisternae that fuse with the tapetal cell membrane and release their contents into the locule. Following completion of the exine, the tapetal cell plastids develop membranebound inclusions with osmiophilic and electron-transparent regions. The plastids undergo ultrastructural changes that suggest breakdown of the inclusion membranes followed by release of their contents into the locule prior to the complete degeneration of the tapetal cells.     

Electron-translucent angular areas in developing tapetum cell walls and pollen grains ofTilia platyphyllos

Summary InTilia platyphyllos, the anther tapetal cell walls undergo significant modifications from the tetrad stage onwards. During the tetrad stage the inner tangential and radial parts of the tapetal walls begin to dissolve, while the distal parts swell. After the tetrad stage, the distal and outer radial tapetal cell walls become covered by a thick, irregular, highly electron-dense, polysaccharide layer. Striking features of the maturing tapetal walls (microspore stage and later) are electron-translucent, structureless, unstainable angular areas of variable dimensions. Similar electron-translucent areas occur in the exine arcades and apertures, but also isolated in the locular fluid ofT. platyphyllos. Electron-translucent areas, that are also found in the exine arcades and tapetal cells of other angiosperms, can be interpreted as the products of poorly understood metabolic processes.     

Secretory tapetum of Brassica oleracea L.: polarity and ultrastructural features

Summary The ultrastructure of the secretory, binucleate tapetum of Brassica oleracea in the micro spore mother cell (MMC) stage through to the mature pollen stage is reported. The tapetal cells differentiate as highly specialized cells whose development is involved in lipid accumulation in their final stage. They start breaking down just before anther dehiscence. Nuclei with dispersed chromatin, large nucleoli and many ribosomes in the cytoplasm characterize the tapetal cells. The wall-bearing tapetum phase ends at the tetrade stage. The dissolution of tapetal walls begins from the inner tangential wall oriented towards the loculus and proceeds gradually along the radial walls to the outer tangential one. The plasmodesmata transversing the radial walls between tapetal cells persist until the mature microspore, long after loss of the inner tangential wall. After wall dissolution, the tapetal protoplasts retain their integrity and position within the anther locule. The tapetal cell membrane is in direct contact with the exine of the microspores/pollen grains and forms tubular evaginations that increase its surface area and appear to be involved in the translocation of solutes from the tapetal cells to the microspores/ pollen grains. The tapetal cells exhibit a polarity expressed by spatial differentiation in the radial direction.     

Ultrastructure of the tapetal cell wall in the stamenless-2 mutant of tomato (Lycopersicon esculentum): correlation between structure and male-sterility

Summary In the stamenless-2 (sl-2) mutant of tomato (Lycopersicon esculentum Mill.), the breakdown in microsporogenesis corresponded with various abnormalities in the ultrastructure of the tapetal cell wall. In some mutant anthers, the inner tangential wall was excessively loosened allowing the passage of tapetal cell wall material and cytoplasmic contents into the anther locule. This presumably altered the osmoticum of the locule and resulted in plasmolysis of the microspores. Membranous fragments commonly observed in the normal tapetal cell wall, and presumed to have a role in transfer of materials from the tapetum to microspores, were absent from thesl-2 mutant. This was associated with reduced transfer of materials, such as lipids, to the developing pollen grains. In addition, a lining of sporopollenin-like deposits that coated the inner tangential wall of the normal tapetum, was discontinuous in the mutant. In mutant anthers where the tapetal cell wall did not loosen, the transfer of all materials was restricted and this resulted in the collapse of sporogenous material.     

Anther, pollen and tapetum development in safflower, Carthamus tinctorius L

In safflower, the anther wall at maturity consists of a single epidermis, an endothecium, a middle layer and the tapetum. The tapetum consists mainly of a single layer of cells. However, this single-layer appearance is punctuated by loci having ‘two-celled’ groupings due to additional periclinal divisions in some tapetal cells. Meiotic division in microsporocytes gives rise to tetrads of microspores. The primexine is formed around the protoplasts of microspores while they are still enveloped within the callose wall. Just prior to microgametogenesis, the microspores enlarge through the process of vacuolation, and the exine wall pattern becomes established. Microgametogenesis results in the formation of 3-celled pollen grains. The two elongated sperm cells appear to be connected. The exine wall is highly sculptured with a distinct tectum, columellae, a foot layer, an endexine and a thin intine. Similar to other members of the Asteraceae family, the tapetum is of the invasive type. The most novel finding of this study is that in addition to the presence of invasive tapetal cells, a small population of ‘non-invasive’ tapetal cells is also present. The tapetal cells next to the anther locules in direct contact with the microspores become invasive and start to grow into the space between developing microspores. These tapetal cells synthesize tryphine and eventually degenerate at the time of gametogenesis releasing their content into the anther locules. A smaller population of non-invasive tapetal cells is formed as a result of periclinal divisions at the time of tapetum differentiation. These cells are not exposed to the anther locules until the degeneration of the invasive tapetal cells. The non-invasive tapetal cells have a different cell fate as they synthesize pollenkitt. This material is responsible for allowing some pollen grains to adhere to each other and to the anther wall after anther dehiscence. This observation explains the out-crossing ability of Carthamus species and varieties in nature.     

珍稀濒危植物大花万代兰的花粉团发育及其分类学意义

万代兰属的属间界限划定及其亲缘关系重建是兰科分类系统中的难解之谜。该研究采用常规石蜡切片技术观察了珍稀濒危植物大花万代兰的一对深裂花粉团的形成机制、花药壁发育模式、小孢子发生及雄配子体发育等的胚胎学特征。结果表明：(1)大花万代兰早期的花药原基分化出一对侧生药室,每个药室的小孢子囊中央分化出一条在花药成熟时会降解的不育隔膜组织,形成两个不等深裂的花粉团。(2)发育完整的花药壁有5~9层,包括2~6层药室内壁,符合多层型花药壁发育类型;绒毡层细胞为单核,腺质型,在花药成熟时,表皮、中层和绒毡层皆降解,仅留下2~6层纤维性加厚的药室内壁。(3)小孢子母细胞经过连续型胞质分裂形成正四面体和左右对称的小孢子四分体,小孢子四分体继续保持在同一个胼胝质内,完成有丝分裂形成了2 细胞型的四合花粉;四合花粉两两紧密排列,且由于隔膜组织的降解,最终发育为一对深裂的花粉团。根据现有兰花花药发育资料,分析了大花万代兰花粉团发育的胚胎学特征的分类学意义,为万代兰属错综复杂的系统分类提供了新资料。     

A contribution to the embryology of Desmodium motorium (Houtt.) Merr. (= D. gyrans (L.f.) DC.) (Fabaceae)

Abstract

The anthers are tetrasporangiate. The anther wall comprises epidermis, fibrous endothecium, middle layer and tapetal layer. The tapetum is of the Glandular type and its cells remain uninucleate. Meiosis in pollen mother cells is normal and simultaneous cytokinesis leads to the formation of tetrahedral and decussate microspore tetrads. The pollen grains are shed at 2-celled stage. The ovule is campylotropous, bitegmic and crassinucellate. Meiosis in megaspore mother cell results in the formation of linear or occasionally T-shaped megaspore tetrad. The chalazal megaspore develops into Monosporic Polygonum type of embryo sac. Endosperm development is of the Nuclear type.     

Microsporogenesis and tapetal development in fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.)

Summary The development of sporogenous and tapetal cells in the anthers of male-fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) plants was studied using light and transmission electron microscopy. In general, male-sterile anthers showed a much greater variability in developmental pattern than male-fertile anthers. The earliest deviation from normal anther development was observed to occur in sterile anthers at meiotic early prophase: there was a degeneration or irregular proliferation of the tapetal cells. Other early aberrant events were the occurrence of numerous small vesicles in the microspore mother cells (MMC) and a disorganized chromatin condensation. Deviations that occurred in sterile anthers at later developmental stages included: (1) less distinct inner structures in the mitochondria of both MMC and tapetal cells from middle prophase onwards. (2) dilated ER and nuclear membranes at MMC prophase, in some cases associated with the formation of protein bodies. (3) breakdown of cell walls in MMCs and tapetal cells at late meiotic prophase. (4) no massive increase in tapetal ER at the tetrad stage. (5) a general dissolution of membranes, first in the MMC, then in the tapetum. (6) abortion of microspores and the occurrence of a plasmodial tapetum in anthers reaching the microspore stage. (7) no distinct degeneration of tapetal cells after microspore formation. Thus, it seems that the factors that lead to abortive microsporogenesis are structurally expressed at widely different times during anther development. Aberrant patterns are not restricted to the tetrad stage but occur at early prophase.     

ABCG26-Mediated Polyketide Trafficking and Hydroxycinnamoyl Spermidines Contribute to Pollen Wall Exine Formation in Arabidopsis

Pollen grains are encased by a multilayered, multifunctional wall. The sporopollenin and pollen coat constituents of the outer pollen wall (exine) are contributed by surrounding sporophytic tapetal cells. Because the biosynthesis and development of the exine occurs in the innermost cell layers of the anther, direct observations of this process are difficult. The objective of this study was to investigate the transport and assembly of exine components from tapetal cells to microspores in the intact anthers of Arabidopsis thaliana. Intrinsically fluorescent components of developing tapetum and microspores were imaged in intact, live anthers using two-photon microscopy. Mutants of ABCG26, which encodes an ATP binding cassette transporter required for exine formation, accumulated large fluorescent vacuoles in tapetal cells, with corresponding loss of fluorescence on microspores. These vacuolar inclusions were not observed in tapetal cells of double mutants of abcg26 and genes encoding the proposed sporopollenin polyketide biosynthetic metabolon (ACYL COENZYME A SYNTHETASE5, POLYKETIDE SYNTHASE A [PKSA], PKSB, and TETRAKETIDE α-PYRONE REDUCTASE1), providing a genetic link between transport by ABCG26 and polyketide biosynthesis. Genetic analysis also showed that hydroxycinnamoyl spermidines, known components of the pollen coat, were exported from tapeta prior to programmed cell death in the absence of polyketides, raising the possibility that they are incorporated into the exine prior to pollen coat deposition. We propose a model where ABCG26-exported polyketides traffic from tapetal cells to form the sporopollenin backbone, in coordination with the trafficking of additional constituents, prior to tapetum programmed cell death.     

Microsporogenesis in Taxus baccata L.: The Formation of the Tetrad and Development of the Microspores

Following meiosis II in Taxus microsporangia a small proportionof the tetrads regularly degenerated. Despite frequent inequalityin the frequency of ribosomes between the spores of a tetrad,partial degeneration within a tetrad was never observed. Theinitial wall of the young spores was found to resemble the wallof the mother cell in containing a fibrillar layer, and thetwo walls may possess similar isolating properties. The symmetryof the tetrad was regularly iso-bilateral. The formation ofthe sporoderm began as the spores were released into the loculusby the rapid dissolution of the wall of the mother cell. Osmiophilicdroplets emerged from the spore protoplast and entered the wall.The fibrillar layer ceased to be recognizable and the dropletscoalesced to form an outer layer on which up to six sporopolleninlamellae, probably of tapetal origin, were deposited. The accretionof a single layer of sporopollenin droplets, in no recognizablepattern, gave rise to the outer verrucose part of the exine.Cytochemical tests showed that the tapetum was rich in acidphosphatases from the beginning of meiosis. Towards the endof its degeneration the tapetum intruded into the loculus andcould therefore be regarded as partly invasive. Taxus baccata, microsporogenesis, tetrad symmetry, sporoderm     

Microsporogenesis in a normal line and in the ogu cytoplasmic male-sterile line of Brassica napus

Summary Under an intermediate temperature regime (23° C/18° C; day/night), microsporogenesis in stamens of the ogu cytoplasmic male-sterile (CMS) line of Brassica napus terminated by the tetrad stage, although in some cases degeneration of the sporogenous tissue occurred prior to meiosis. In most cases the tetrads were collapsed and bounded by a sparse exine, but contained many organelles. Also, the tapetum in CMS anthers was abnormal and often highly vacuolated by the tetrad stage. Under low temperature conditions (18° C/15° C; day/night), neither microsporogenous nor tapetal tissues were observed. In the normal stamens, no differences were observed under different temperature regimes. In conjunction with the adjoining paper, this study demonstrates that temperature conditions strongly affect the cytological processes associated with microsporogenesis in the CMS anthers.     

Distribution of cellulosic wall in the anthers of Arabidopsis during microsporogenesis

Key message

Cellulose-specific staining revealed that tapetal cells and microsporocytes lose cellulosic walls before the onset of meiosis. Cellulosic wall degradation in microsporocytes might be independent of tapetal cells (or TPD1).

Abstract

Some cell types in a variety of angiosperms have been reported to lack cell walls. Here, we report that the tapetal cells of the anther of Arabidopsis thaliana did not appear to have a cellulosic wall based on staining with Calcofluor and Renaissance 2200. During sporogenous cell formation, cellulosic wall was present in all anther tissues. However, before meiosis it was almost absent on the tapetal cells and on the microsporocytes. In a sporocyteless/nozzle (spl/nzz) mutant, which lacks several components (microsporocytes, tapetum, middle layer and endothecium), cellulosic wall was detected in all anther cells. In another mutant, tapetum determinant1 (tpd1), which lacks tapetum and has more microsporocytes, cellulosic wall was almost absent on the microsporocytes before meiosis, similar to the wild type. These results suggest that the tapetum cells and microsporocytes lose cellulosic walls during microsporocyte formation, and that cell wall degradation occurs downstream of SPL/NZZ and is independent of TPD1.     

Invasive tapetum and tricelled pollen inAmbrosia trifida (Asteraceae,tribeHeliantheae)

Staminate flowers of giant ragweed,Ambrosia trifida L. (Asteraceae, tribeHeliantheae, subtribeAmbrosiinae) were processed into resin and sectioned 1–2 µm thick. The invasive (amoeboid) anther tapetum remains parietal until microspores are released from tetrads, then it swells and invades the locule, merging gradually into a single protoplast that flows among the microspores. After the tapetal membrane ruptures at late microspore stage, tapetal debris fills the locule, then disappears as pollen matures. Pollen becomes tricelled before anthesis. The two sperm cell nuclei are slender and wormlike. The present report supports the two generalizations that invasive tapetum and tricelled pollen are attributes of theAsteraceae.     

POLLEN WALL AND TAPETAL ORBICULAR WALL DEVELOPMENT IN SORGHUM BICOLOR (GRAMINEAE)

Pollen wall development in Sorghum bicolor is morphologically and temporally paralleled by the formation of a prominent orbicular wall on the inner tangential surface of the tapetum. In the late tetrad stage, a thin, nearly uniform primexine forms around each microspore (except at the pore site) beneath the intact callose; concurrently, small spherical bodies (pro-orbicules) appear between the undulate tapetal plasmalemma and the disappearing tapetal primary wall. Within the primexine, differentially staining loci appear, which only develop into young bacula as the callose disappears. Thus, microspore walls are devoid of a visible exine pattern when released from tetrads. Afterwards, sporopollenin accumulates simultaneously on the primexine and bacula, forming the exine, and on the pro-orbicules, forming orbicules. Channels develop in the tectum and nexine, and both layers thicken to complete the microspore exine. Channeled sporopollenin also accumulates on the orbicules. A prominent sporopollenin reticulum interconnects the individual orbicules to produce an orbicular wall; this wall persists even after the tapetal protoplasts degenerate and after anthesis. While the pollen grains become engorged with reserves, a thick intine, containing conspicuous cytoplasmic channels, forms beneath the exine. Fibrous material collects beneath the orbicular wall. The parallel development and morphological similarities between the tapetal and pollen walls are discussed.     

山麦冬大小孢子发生及雌雄配子体发育研究

采用石蜡切片技术对百合科植物山麦冬大小孢子发生及雌雄配子体发育进行了观察研究。结果表明:(1)山麦冬花药具有4个花粉囊,花药壁的发育方式为基本型,花药壁完全分化时由表皮、药室内壁、中层及绒毡层组成。(2)绒毡层发育类型为分泌型,到四分体孢子彼此分离形成单细胞花粉阶段,绒毡层细胞开始解体退化,花粉成熟时绒毡层细胞完全消失;花粉母细胞减数分裂为连续型,四分体为左右对称形排列,成熟花粉为3-细胞花粉,单萌发沟。(3)子房3室,每室2枚胚珠,胚珠倒生型,双珠被,薄珠心,雌性孢原细胞不经过平周分裂而直接发育而成大孢子母细胞。(4)减数分裂后四分体大孢子呈线型或T型排列,合点端大孢子分化为功能大孢子,胚囊发育为蓼型;花粉母细胞减数分裂过程中,二分体、四分体细胞外方被胼胝质壁所包被,小孢子形成后胼胝质壁逐渐消失。该研究结果丰富了百合科植物生殖生物学研究的内容,也为探讨百合科植物的系统学研究提供了参考。     

A histochemical and ultrastructural study of the ontogeny and differentiation of pollen inPodocarpus macrophyllus D. Don

Summary Male cones ofPodocarpus macrophyllus D. Don enter a period of dormancy lasting almost a year after the differentiation of archesporial tissue. The cell walls of the sporogenous and tapetal cells are different in composition from those of the cells comprising the wall of the microsporangium. The walls of tapetal cells undergo complete dissolution but the naked protoplasts do not invade the cavity of the microsporangium, and eventually degeneratein situ. Sporopollenin-containing bodies are formed on the tapetal plasmalemma although no specific tapetal organelles can be singled out as sites of synthesis of sporopollenin precursors. The original walls of the microspore mother cells are broken down completely and replaced by a thin callose-like wall. No cytomictic channels are formed prior to or during early meiosis. The outer nuclear membrane of the sporogenous cells forms numerous vesicles which likely play an important role in preparing the cell for meiosis and in the breakdown of the original sporogenous cell wall and the formation of the new wall. Pronounced evaginations and invaginations of the nuclear envelope during the tetrad stage are seen which again indicate vital nucleo-cytoplasmic exchange at the time when species specific sexine layer is being laid down. The microspore protoplast synthesizes a portion of sporopollenin precursors. Sexine and part of nexine I are laid down during the tetrad stage on lamellae of unit membrane dimensions while nexines II and III are formed after the dissolution of the tetrads by the coalescence of small, electron dense particles. Cells of the male gametophyte are initially separated from each other by distinct cell walls often traversed by plasmodesmata. Mature pollen grains have appreciable reserves of protein, lipid and starch. Results of histochemical and scanning electron microscopical observations are also reported and discussed.     

A comparative light and electron microscopic analysis of microspore and tapetum development in fertile and cytoplasmic male sterile radish

To gain further insight into the abortive stages and ultrastructural changes leading to pollen degeneration of a novel cytoplasmic male sterile radish 805A, we compared differences of cellular and subcellular structure of sterile anther with fertile anther by light and electron microscopy analysis. Two types of locule degeneration in sterile anther were detected, of which the time of degeneration occurred and completed was different. In type I, abnormality of pollen mother cells (PMCs) and tapetal cells, including condensation of cytoplasm and large vacuoles within tapetal cells, was shown at PMC stage. In type II, meiosis and early tetrad stage progressed normally except for large vacuoles that appeared in tapetal cells. Ultrastructural alterations of the cellular organization were observed in the type II locules, such as chromatin condensation at the periphery of the nucleus and degeneration of the karyotheca, compared with normal pollen development. The results suggested that the cytoplasmic male sterility anther degeneration was probably caused by dysfunctions of tapetum and vacuolation of tapetum, PMCs, and microspores. Thus, the identical factors, which induced CMS in the same cytoplasmic and nuclear genetic background, might affect development of tapetum and microspore at different stages during the cytoplasmic male sterile 805A anther development.