Camellia oleifera is an important plant species that produces edible oils. Understanding the double fertilization of this plant is critical for studies concerning crossbreeding, self-incompatibility, and the biological mechanisms underlying hybridization. We aimed to characterize pollen tube growth and double fertilization in C. oleifera. The female and male parent cultivars (Huashuo and Xianglin XLC15, respectively) were used for artificial pollination. Growth of the pollen tube in the style, ovary, and ovule from pollination to fertilization and the cytological characteristics of female and male gamete fusion during double fertilization were observed using fluorescence and scanning electron microscopy (SEM). Numerous pollen grains germinated 2 to 4 hours after pollination. The pollen tubes entered the interspaces between the papillar cells, grew along the stylar canal, and aggregated at the one-third site of the style. They grew in the gradually narrowing stylar canal, entering the locule. The tubes turned 90° and entered the embryo sac through the micropyle; subsequently, they entered a degenerated synergid, where the spermatids were released. One sperm nucleus fused with the polar nucleus, forming the primary endosperm nucleus, whereas the other sperm fused with the egg, forming the zygote. The polar nucleus was fertilized earlier than the egg. Double fertilization of C. oleifera is characterized as pre-mitotic gametogony. The current results lay a theoretical foundation for studies concerning the crossbreeding and embryology of C. oleifera and provide fundamental data concerning the reproductive biology of the genus Camellia.
Chao Gao, Deyi Yuan, Ya Yang, Bifang Wang, Dongming Liu, and Feng Zou
Bin Cai, Cheng-Hui Li, Ai-Sheng Xiong, Ri-He Peng, Jun Zhou, Feng Gao, Zhen Zhang, and Quan-Hong Yao
The database of grape transcription factors (DGTF) is a plant transcription factor (TF) database comprehensively collecting and annotating grape (Vitis L.) TF. The DGTF contains 1423 putative grape TF in 57 families. These TF were identified from the predicted wine grape (Vitis vinifera L.) proteins from the grape genome sequencing project by means of a domain search. The DGTF provides detailed annotations for individual members of each TF family, including sequence feature, domain architecture, expression information, and orthologs in other plants. Cross-links to other public databases make its annotations more extensive. In addition, some other transcriptional regulators were also included in the DGTF. It contains 202 transcriptional regulators in 10 families.
Feng Gao, Arvind H. Hirani, Jun Liu, Zheng Liu, Guohua Fu, Chunren Wu, Peter B.E. McVetty, and Genyi Li
There are various clubroot pathogen (Plasmodiophora brassicae) resistance genes within Brassica species with european turnip (B. rapa ssp. rapifera) being identified as potentially the best source of resistance for the development of clubroot-resistant cultivars in chinese cabbage (B. rapa ssp. pekinensis). To use clubroot resistance genes effectively, it is necessary to map these genes so that molecular markers inside or closely linked to these resistance genes can be developed. Using molecular marker-assisted selection, the clubroot resistance genes can be effectively transferred from cultivar to cultivar and from species to species. In this report, one clubroot resistance locus was mapped on linkage group A3 using five segregating populations developed from five chinese cabbage cultivars, suggesting that all the five cultivars shared the same clubroot resistance locus. Furthermore, one of these five chinese cabbage cultivars was used to develop a large segregating population to fine-map this clubroot resistance locus to a 187-kilobp chromosomal region. Molecular markers that are closely linked to the mapped clubroot resistance locus have been developed that can be used for marker-assisted selection in chinese cabbage and canola/rapeseed (B. rapa and B. napus) breeding programs.