植物學(xué)

來(lái)源出版物：Journal of Integrative Plant Biology，2014，56（12）: 1118-1124聯(lián)系郵箱：Daniel Marino，daniel.marino@ehu.es

封面介紹：Legume-Rhizobium interactions are governed by both local and systemic signals. In this issue，Larrainzar et al.（pp. 1118-1124）provide a comprehensive overview on the application of splitroot systems to understand the systemic or local signaling involved in symbiosis establishment，nodule number and nitrogen fixation under a variety of stress conditions.

Split-root systems applied to the study of the legume-rhizobial symbiosis：What have we learned？

Estíbaliz Larrainzar，Erena Gil-Quintana，Cesar Arrese-Igor，et al.

Split-root system（SRS）approaches allow the differential treatment of separate and independent root systems，while sharing a common aerial part. As such，SRS is a useful tool for the discrimination of systemic（shoot origin）versus local（root/nodule origin）regulation mechanisms. This type of approach is particularly useful when studying the complex regulatory mechanisms governing the symbiosis established between legumes and Rhizobium bacteria. The current work provides an overview of the main insights gained from the application of SRS approaches to understand how nodule number（nodulation autoregulation）and nitrogen fixation are controlled both under non-stressful conditions and in response to a variety of stresses. Nodule number appears to be mainly controlled at the systemic level through a signal which is produced by nodule/root tissue，translocated to the shoot，and transmitted back to the root system，involving shoot Leu-rich repeat receptor-like kinases. In contrast，both local and systemic mechanisms have been shown to operate for the regulation of nitrogenase activity in nodules. Under drought and heavy metal stress，the regulation is mostly local，whereas the application of exogenous nitrogen seems to exert a regulation of nitrogen fixation both at the local and systemic levels.

legume-rhizobia；nitrogen fixation；nodulation；split-root system；symbiosis