Department of Mathematics and Statistics, University of Minnesota Duluth, Duluth, Minnesota, United States of America.
PLoS One. 2010 Jan 20;5(1):e8782. doi: 10.1371/journal.pone.0008782.
Nectaries are the floral organs responsible for the synthesis and secretion of nectar. Despite their central roles in pollination biology, very little is understood about the molecular mechanisms underlying nectar production. This project was undertaken to identify genes potentially involved in mediating nectary form and function in Brassica rapa.
Four cDNA libraries were created using RNA isolated from the median and lateral nectaries of B. rapa flowers, with one normalized and one non-normalized library being generated from each tissue. Approximately 3,000 clones from each library were randomly sequenced from the 5' end to generate a total of 11,101 high quality expressed sequence tags (ESTs). Sequence assembly of all ESTs together allowed the identification of 1,453 contigs and 4,403 singleton sequences, with the Basic Localized Alignment Search Tool (BLAST) being used to identify 4,138 presumptive orthologs to Arabidopsis thaliana genes. Several genes differentially expressed between median and lateral nectaries were initially identified based upon the number of BLAST hits represented by independent ESTs, and later confirmed via reverse transcription polymerase chain reaction (RT PCR). RT PCR was also used to verify the expression patterns of eight putative orthologs to known Arabidopsis nectary-enriched genes.
CONCLUSIONS/SIGNIFICANCE: This work provided a snapshot of gene expression in actively secreting B. rapa nectaries, and also allowed the identification of differential gene expression between median and lateral nectaries. Moreover, 207 orthologs to known nectary-enriched genes from Arabidopsis were identified through this analysis. The results suggest that genes involved in nectar production are conserved amongst the Brassicaceae, and also supply clones and sequence information that can be used to probe nectary function in B. rapa.
蜜腺是负责合成和分泌花蜜的花器官。尽管它们在传粉生物学中起着核心作用，但对花蜜产生的分子机制却知之甚少。本项目旨在鉴定可能参与介导芸薹属油菜蜜腺形态和功能的基因。
使用从中等和侧蜜腺分离的 RNA 构建了四个 cDNA 文库，每个组织分别生成一个归一化和非归一化文库。从每个文库中随机测序约 3000 个克隆从 5'端生成总共 11101 个高质量表达序列标签（EST）。所有 EST 的序列组装允许鉴定 1453 个 contigs 和 4403 个单序列，使用基本局部比对搜索工具（BLAST）鉴定 4138 个拟南芥基因的假定直系同源物。最初根据独立 EST 代表的 BLAST 命中数鉴定了几个在中蜜腺和侧蜜腺之间差异表达的基因，然后通过逆转录聚合酶链反应（RT-PCR）进一步确认。RT-PCR 还用于验证八个已知拟南芥蜜腺富集基因的推定直系同源物的表达模式。
结论/意义：这项工作提供了活跃分泌的芸薹属油菜蜜腺中基因表达的快照，也鉴定了中蜜腺和侧蜜腺之间的差异基因表达。此外，通过该分析鉴定了 207 个与已知拟南芥蜜腺富集基因的直系同源物。结果表明，参与花蜜产生的基因在十字花科中是保守的，并且还提供了可以用于探测芸薹属油菜蜜腺功能的克隆和序列信息。
