Aloni Roni, Aloni Erez, Langhans Markus, Ullrich Cornelia I
Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Planta. 2006 Jan;223(2):315-28. doi: 10.1007/s00425-005-0088-9. Epub 2005 Oct 6.
To elucidate the role of auxin in flower morphogenesis, its distribution patterns were studied during flower development in Arabidopsis thaliana (L.) Heynh. Expression of DR5::GUS was regarded to reflect sites of free auxin, while immunolocalization with auxin polyclonal antibodies visualized conjugated auxin distribution. The youngest flower bud was loaded with conjugated auxin. During development, the apparent concentration of free auxin increased in gradual patterns starting at the floral-organ tip. Anthers are major sites of high concentrations of free auxin that retard the development of neighboring floral organs in both the acropetal and basipetal directions. The IAA-producing anthers synchronize flower development by retarding petal development and nectary gland activity almost up to anthesis. Tapetum cells of young anthers contain free IAA which accumulates in pollen grains, suggesting that auxin promotes pollen-tube growth towards the ovules. High amounts of free auxin in the stigma induce a wide xylem fan immediately beneath it. After fertilization, the developing embryos and seeds show elevated concentrations of auxin, which establish their axial polarity. This developmental pattern of auxin production during floral-bud development suggests that young organs which produce high concentrations of free IAA inhibit or retard organ-primordium initiation and development at the shoot tip.
为阐明生长素在花形态发生中的作用，研究了其在拟南芥花发育过程中的分布模式。DR5::GUS的表达被视为反映游离生长素的位点，而用生长素多克隆抗体进行免疫定位则可观察到结合态生长素的分布。最幼嫩的花芽富含结合态生长素。在发育过程中，游离生长素的表观浓度从花器官顶端开始呈逐渐增加的模式。花药是游离生长素高浓度的主要位点，在向顶和向基方向均会抑制相邻花器官的发育。产生吲哚 - 3 - 乙酸（IAA）的花药通过几乎延迟花瓣发育和蜜腺活动直至开花来同步花的发育。幼嫩花药的绒毡层细胞含有游离IAA，其在花粉粒中积累，这表明生长素促进花粉管向胚珠生长。柱头中大量的游离生长素在其正下方诱导形成宽的木质部扇形结构。受精后，发育中的胚和种子显示出生长素浓度升高，这确立了它们的轴向极性。花芽发育过程中生长素产生的这种发育模式表明，产生高浓度游离IAA的幼嫩器官会抑制或延迟茎尖器官原基的起始和发育。
