Anatomical Characteristics of Petalized Anther Abortion in Male Sterile Camellia oleifera Plants

Abstract

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.

Abnormal Calcium Accumulation and ROS Homeostasis-Induced Tapetal Programmed Cell Death Lead to Pollen Abortion of Petaloid-Type Cytoplasmic Male Sterility in Camellia oleifera

“…The petaloid-type CMS in C. oleifera 'X1' has also been reported in previous studies [10]. The anthers of petaloid-type male-sterile C. oleifera plants produce little or no pollen, which is helpful for leveraging heterosis as female parents [10,11]. Thus, understanding the mechanism of male sterility through the study of abortive anthers contributes to improving the traditional breeding strategies of C. oleifera.…”

“…Previous studies have reported that the petalized male sterility of C. oleifera may be related to premature or late degradation of the tapetum [10,11]. However, the physiology of calcium accumulation and reactive oxygen species during abortive anther development remains unclear.…”

Isolation, purification and PEG-mediated transient expression of mesophyll protoplasts in Camellia oleifera

“…C. oleifera is a widely distributed plant species in southern China [ 1 ], with a planting area of more than 4.5 million hectares [ 48 ]. The C. oleifera industry is rapidly expanding and developing, becoming one of the main industries for rural revitalization in China [ 4 ].…”

The True Identity of the “Second Pollen Morphology” of Camellia oleifera—Stomium Cells

“…Pollen is a crucial carrier of genetic information in angiosperms and is released from the pollen sac after anther dehiscence [1][2][3]. Pollen morphology is strictly genetically regulated, and the pollen of different species or varieties has certain morphological recognition features that are widely employed in studies such as taxonomy or palynology [4,5].…”

“…Early studies have shown that C. oleifera pollen viability is as high as 83% [18,19]. However, later studies on C. oleifera asexual lines showed pollen viability ranging from 40 to 60% [1,10,17,20,21]. It thus appears that the yield-oriented selection in the breeding process reduces the pollen viability of the selected C. oleifera varieties.…”