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Cytoplasmic male sterility (CMS) plays a crucial role in the utilization of heterosis. The petaloid anther abortion in oil tea (Camellia oleifera Abel.) constitutes a CMS phenomenon, which is of great value for the hybrid breeding of oil tea. However, as the mechanism of its CMS is still poorly understood, it is necessary to study the cytology and physiological characteristics of anther abortion. In this study, a C. oleifera cultivar, Huashuo (HS), and its petalized CMS mutant (HSP) were used as materials to explore this mechanism. Compared with HS, cytological analysis demonstrated that HSP showed early-onset tapetum programmed cell death (PCD) and an organelle disorder phenotype during the tetrad stage. In HSP, anthers exhibited elevated levels of calcium deposition in anther wall tissues, tapetum layers, and microspores, and yet calcium accumulation was abnormal at the later stage. The contents of hydrogen peroxide and MDA in HSP anthers were higher, and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were lower than those of HS, which resulted in an excessive accumulation of reactive oxygen species (ROS). Real-time quantitative PCR confirmed that the transcription levels of CoPOD and CoCAT genes encoding key antioxidant enzymes in HSP were downregulated compared with HS in early pollen development; the gene CoCPK, which encodes a calcium-dependent protein kinase associated with antioxidase, was upregulated during the critical period. Thus, we suggest that excessive ROS as a signal breaks the balance of the antioxidant system, and along with an abnormal distribution of calcium ions, leads to the early initiation of PCD in the tapetum, and ultimately leads to pollen abortion for HSP. These results lay a cytological and physiological foundation for further studies on the CMS mechanism, and provide information for breeding male-sterile lines of C. oleifera. [ABSTRACT FROM AUTHOR]

Cytoplasmic male sterility (CMS) plays a crucial role in the utilization of heterosis. The petaloid anther abortion in oil tea (Camellia oleifera Abel.) constitutes a CMS phenomenon, which is of great value for the hybrid breeding of oil tea. However, as the mechanism of its CMS is still poorly understood, it is necessary to study the cytology and physiological characteristics of anther abortion. In this study, a C. oleifera cultivar, Huashuo (HS), and its petalized CMS mutant (HSP) were used as materials to explore this mechanism. Compared with HS, cytological analysis demonstrated that HSP showed early-onset tapetum programmed cell death (PCD) and an organelle disorder phenotype during the tetrad stage. In HSP, anthers exhibited elevated levels of calcium deposition in anther wall tissues, tapetum layers, and microspores, and yet calcium accumulation was abnormal at the later stage. The contents of hydrogen peroxide and MDA in HSP anthers were higher, and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were lower than those of HS, which resulted in an excessive accumulation of reactive oxygen species (ROS). Real-time quantitative PCR confirmed that the transcription levels of CoPOD and CoCAT genes encoding key antioxidant enzymes in HSP were downregulated compared with HS in early pollen development; the gene CoCPK, which encodes a calcium-dependent protein kinase associated with antioxidase, was upregulated during the critical period. Thus, we suggest that excessive ROS as a signal breaks the balance of the antioxidant system, and along with an abnormal distribution of calcium ions, leads to the early initiation of PCD in the tapetum, and ultimately leads to pollen abortion for HSP. These results lay a cytological and physiological foundation for further studies on the CMS mechanism, and provide information for breeding male-sterile lines of C. oleifera.

Petalized anther abortion is an important characteristic of male sterility in plants. The male sterile plants (HB-21) evincing petalized anther abortion previously discovered in a clone population of the Camellia oleifera cultivar Huashuo by our research group were selected as the experimental material in this study. Using plant microscopy and anatomic methods and given the correspondence between external morphology and internal structure, we studied the anatomic characteristics of petalized anther abortion (with a fertile plant as the control group) in various stages, from flower bud differentiation to anther maturity, in hopes of providing a theoretical basis for research on and applications of male sterile C. oleifera plants, a new method for the selection of male sterile C. oleifera cultivars, and improvements in the yield and quality of C. oleifera. In this study, the development of anthers in C. oleifera was divided into 14 stages. Petalized anther abortion in male sterile plants was mainly initiated in the second stage (the stage of sporogenous cells). Either the petalized upper anther parts did not form pollen sacs, or the entire anthers did not form pollen sacs. The lower parts of some anthers could form deformed pollen sacs and develop, and these anthers could be roughly divided into two types: fully and partially petalized anthers. Abnormal callose and the premature degradation of the tapetum occurred in the pollen sacs formed by partially petalized anthers during the development process, resulting in the absence of inclusions in the pollen grains formed. Small quantities of mature pollen grains withered inward from the germinal furrows, exhibiting obvious abortion characteristics. The relative in vitro germination rate of the pollen produced by the partially petalized anthers of sterile plants was 11.20%, and the relative activity of triphenyltetrazolium chloride was 3.24%, while the fully petalized anthers did not generate pollen grains. Either the petalized anthers in male sterile plants did not produce pollen, or the vitality of the small amounts of pollen produced by sterile plants was very low compared with that of fertile plants. Such male sterile plants could be used to select correct clones and have good prospects for application in production.

The inflorescence of Hedychium coccineum Smith is thyrse, and the primary bracts are initiated in a spiral phyllotactic pattern on the sides of the inflorescence dome. Cincinnus primordia are initiated on the flank of the inflorescence apex, in the axils of primary bracts. This primordium subsequently develops a bract and a floral primordium. Then, the floral primordium enlarges, flattens apically, and becomes rounded. Sepals are initiated sequentially from the rounded corner of the primordium ring sepal initiation, and the floral primordium continues to enlarge and produces a ring primordium. Later, this ring primordium separates three common primordia surrounding a central cavity. The adaxial common primordium is the first separation. This primordium produces the posterior petal and the fertile stamen. The remaining two common primordia separate and produce respectively a petal and a petaloid, the inner androecial member. As the flower enlarges, the cavity of the floral cup becomes a rounded-triangular apex; these apices are the sites of outer androecial primordium initiation. The abaxial outer androecial member slightly forms before the two adaxial members develop. But this primordium ceases growth soon after initiation, while the two posterior primordia continue growth to produce the lateral petaloid staminodes. During this stage, gynoecial initiates in the floral cup and continues to grow until extending beyond the labellum. [ABSTRACT FROM AUTHOR]