本期封面所示为豌豆（Pisum sativum）的一种分枝能力增强的突变体的叶基中的一个生长中的芽子。
多年来，教科书上都说有五种“经典”的植物激素：生长素（auxin）、赤霉素（gibberellin）、乙烯（ethylene）、细胞分裂素（cytokinin） 和脱落酸（abscisic acid）。在这个清单上还可添上油菜素甾醇类化合物（brassinosteroids）、一氧化氮（nitric oxide） 和茉莉酸类化合物（jasmonates）等，它们被称为植物激素（phytohormones），也叫植物生长调节素。
植物枝条的形成由激素调控，生长素和细胞分裂素在其中都发挥作用。但几个物种中分枝能力增强的突变体的存在表明，这其中涉及第三个因子，即一种从根部释放出的新的植物激素，它能防止过度分枝。现在，两个小组识别出了一类被称为strigolactones的化合物（或它们的衍生物之一）为这种新的激素。Strigolactones是在根系分泌物中发现的，在分枝突变体中含量减少；这些化合物的外部施用在突变体中抑制枝条的形成。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 455, 189-194 (11 September 2008) | doi:10.1038/nature07271
Strigolactone inhibition of shoot branching
Victoria Gomez-Roldan1, Soraya Fermas2, Philip B. Brewer3, Virginie Puech-Pagès1, Elizabeth A. Dun3, Jean-Paul Pillot2, Fabien Letisse4, Radoslava Matusova5, Saida Danoun1, Jean-Charles Portais4, Harro Bouwmeester5,6, Guillaume Bécard1, Christine A. Beveridge3,7,8, Catherine Rameau2,8 & Soizic F. Rochange1,8
1 Université de Toulouse; UPS; CNRS; Surface Cellulaire et Signalisation chez les Végétaux, 24 chemin de Borde Rouge, F-31326 Castanet-Tolosan, France
2 Station de Génétique et d'Amélioration des Plantes, Institut J. P. Bourgin, UR254 INRA, F-78000 Versailles, France
3 ARC Centre of Excellence for Integrative Legume Research, The University of Queensland, Brisbane 4072, Australia
4 CNRS, UMR5504, INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, INSA de Toulouse, F-31400 Toulouse, France
5 Plant Research International, PO Box 16, 6700 AA Wageningen, the Netherlands
6 Laboratory of Plant Physiology, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, the Netherlands
7 School of Integrative Biology, The University of Queensland, Brisbane 4072, Australia
8 These authors contributed equally to this work.
A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants. Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis. In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal symbiosis and parasitic weed interaction.
