Qin Yuan, Leydon Alexander R, Manziello Ann, Pandey Ritu, Mount David, Denic Stojan, Vasic Bane, Johnson Mark A, Palanivelu Ravishankar
Department of Plant Sciences, University of Arizona, Tucson, Arizona, United States of America.
PLoS Genet. 2009 Aug;5(8):e1000621. doi: 10.1371/journal.pgen.1000621. Epub 2009 Aug 28.
Pollen tubes extend through pistil tissues and are guided to ovules where they release sperm for fertilization. Although pollen tubes can germinate and elongate in a synthetic medium, their trajectory is random and their growth rates are slower compared to growth in pistil tissues. Furthermore, interaction with the pistil renders pollen tubes competent to respond to guidance cues secreted by specialized cells within the ovule. The molecular basis for this potentiation of the pollen tube by the pistil remains uncharacterized. Using microarray analysis in Arabidopsis, we show that pollen tubes that have grown through stigma and style tissues of a pistil have a distinct gene expression profile and express a substantially larger fraction of the Arabidopsis genome than pollen grains or pollen tubes grown in vitro. Genes involved in signal transduction, transcription, and pollen tube growth are overrepresented in the subset of the Arabidopsis genome that is enriched in pistil-interacted pollen tubes, suggesting the possibility of a regulatory network that orchestrates gene expression as pollen tubes migrate through the pistil. Reverse genetic analysis of genes induced during pollen tube growth identified seven that had not previously been implicated in pollen tube growth. Two genes are required for pollen tube navigation through the pistil, and five genes are required for optimal pollen tube elongation in vitro. Our studies form the foundation for functional genomic analysis of the interactions between the pollen tube and the pistil, which is an excellent system for elucidation of novel modes of cell-cell interaction.
花粉管穿过雌蕊组织并被引导至胚珠，在那里它们释放精子进行受精。尽管花粉管可以在合成培养基中萌发和伸长，但其轨迹是随机的，与在雌蕊组织中的生长相比，其生长速度较慢。此外，与雌蕊的相互作用使花粉管能够对胚珠内特化细胞分泌的引导信号作出反应。雌蕊对花粉管这种增强作用的分子基础仍未明确。通过对拟南芥进行微阵列分析，我们发现，已经穿过雌蕊柱头和花柱组织生长的花粉管具有独特的基因表达谱，并且与在体外生长的花粉粒或花粉管相比，表达了拟南芥基因组中相当大比例的基因。参与信号转导、转录和花粉管生长的基因在富含与雌蕊相互作用的花粉管的拟南芥基因组子集中过度表达，这表明在花粉管穿过雌蕊迁移过程中，可能存在一个协调基因表达的调控网络。对花粉管生长过程中诱导表达的基因进行反向遗传学分析，鉴定出七个以前未涉及花粉管生长的基因。两个基因是花粉管穿过雌蕊导航所必需的，五个基因是花粉管在体外最佳伸长所必需的。我们的研究为花粉管与雌蕊相互作用的功能基因组分析奠定了基础，这是阐明细胞间相互作用新模式的一个极佳系统。
