Brassica campestris male fertility 19 （BcMF19; GenBank accession number GQ902048.1）, a gene that is specially expressed in tapetum cells and microspores during anther development in B. campestris ssp. chinensis, which is learned from the previous in situ hybridization study. In the present study, we constructed antisense-silenced plants of BcMF19 using B. campestris ssp. chinensis to validate this prediction. The morphology of the pistils, long anthers, and short anthers was significantly affected in 35sbcmf19 compared with the control samples. 4＇-6-Diamidino-2-phenylindole staining revealed that two generative nuclei and one large vegetative nucleus were not affected in the mutant compared with control. Statistical analysis of Alexander＇s staining results showed that 96% of the control pollen grains had vitality, whereas only 86% of the mutant pollen grains did. Under scanning electron microscopy, the mutant demonstrated numerous abnormal pollen grains and resembled dried persimmon. The frequency of normal pollen grains was approximately 18%. Under transmission electron microscopy, the pollen intine during the binucleate and mature pollen stages in 35sbcmf19 exhibited abnormal thickening, especially at the germinal furrows, compared with control. In vitro pollen germination test showed that the tips of the mutant pollen tubes transformed into globular alveoli and stopped growing compared with control. On the other hand, in vivo pollen germination test suggested that BcMF19 affected the pollen tube extension in the pistil. These findings indicate that BcMF19 is essential to the pollen development and pollen tube extension orB. campestris ssp. chinensis.
Plant trichomes serve as a highly suitable model for investigating cell differentiation at the single-cell level. The regulatory genes involved in unicellular trichome develop- ment in Arabidopsis thaliana have been intensively studied, but genes regulating multicellular trichome development in plants remain unclear. Here, we characterized Cucumis sativus （cucumber） trichomes as representative multicellular and unbranched structures, and identified Micro-trichome （Mict）, using map-based cloning in an F2 segregating population of 7,936 individuals generated from a spontaneous mict mutant. In mitt plants, trichomes in both leaves and fruits, are small, poorly developed, and denser than in the wild type. Sequence analysis revealed that a 2,649-bp genomic deletion, spanning the first and second exons, occurred in a plant-specific class I homeodomain-leucine zipper gene. Tissue-specific expression analysis indicated that Mict is strongly expressed in the trichome cells. Transcriptome profiling identified potential targets of Mict including putative homologs of genes known in other systems to regulate trichome development, meristem determinacy, and hormone responsiveness. Phylo- genic analysis charted the relationships among putative homologs in angiosperms. Our paper represents initial steps toward understanding the development of multicellular trichomes.
Jun-Long ZhaoJun-Song PanYuan GuanWei-Wei ZhangBei-Bei BieYun-Li WangHuan-Le HeHong-Li LianRun Cai
