Crespi Martin, Frugier Florian
Institut des Sciences du Végétal (ISV), Centre National de la Recherche Scientifique, 91198 Gif sur Yvette cedex, France.
Sci Signal. 2008 Dec 9;1(49):re11. doi: 10.1126/scisignal.149re11.
The symbiotic interaction between Rhizobium bacteria and legume plants leads to the induction of a new developmental program: the formation of nitrogen-fixing root nodules. Nodulation is triggered by specific bacterial signals, the Nod factors, and integrates plant developmental regulatory pathways to reactivate differentiated cortical cells. This results in the formation of a de novo meristem, corresponding to a plant stem cell niche. Recent data have shown a crucial function of the phytohormone cytokinin and its signaling pathway in nodule initiation. Activation of either cytokinin or components of the Nod factor signaling pathway leads to spontaneous induction of the nodule organogenesis program. These genetic analyses have been complemented with genomic studies of transcriptional networks activated during early nodulation. Transcriptional and posttranscriptional regulation, notably involving transcription factors and microRNAs, fine-tune the dynamic equilibrium between proliferating meristematic and differentiated nitrogen-fixing cells. The recent identification of these regulatory mechanisms has helped elucidate nodule organogenesis and the agriculturally relevant process of symbiotic nitrogen fixation and extended our understanding of how differentiated root cells acquire developmental plasticity to form a new organ.
固氮根瘤的形成。结瘤由特定的细菌信号——根瘤因子触发，并整合植物发育调控途径以重新激活分化的皮层细胞。这导致了一个从头形成的分生组织的形成，它对应于植物干细胞生态位。最近的数据表明，植物激素细胞分裂素及其信号通路在根瘤起始中具有关键作用。细胞分裂素或根瘤因子信号通路的组分的激活都会导致根瘤器官发生程序的自发诱导。这些遗传学分析已通过对早期结瘤过程中激活的转录网络的基因组研究得到补充。转录和转录后调控，特别是涉及转录因子和微小RNA的调控，微调了增殖的分生组织细胞和分化的固氮细胞之间的动态平衡。这些调控机制的最新鉴定有助于阐明根瘤器官发生以及共生固氮这一与农业相关的过程，并扩展了我们对分化的根细胞如何获得发育可塑性以形成新器官的理解。
