Jacob Blaustein Institutes for Desert Research, French Associates Institute for Agriculture and Biotechnology of Drylands, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, 84990, Israel.
J Exp Bot. 2010;61(1):211-24. doi: 10.1093/jxb/erp290.
Plant roots exhibit remarkable developmental plasticity in response to local soil conditions. It is shown here that mild salt stress stimulates a stress-induced morphogenic response (SIMR) in Arabidopsis thaliana roots characteristic of several other abiotic stresses: the proliferation of lateral roots (LRs) with a concomitant reduction in LR and primary root length. The LR proliferation component of the salt SIMR is dramatically enhanced by the transfer of seedlings from a low to a high NO3- medium, thereby compensating for the decreased LR length and maintaining overall LR surface area. Increased LR proliferation is specific to salt stress (osmotic stress alone has no stimulatory effect) and is due to the progression of more LR primordia from the pre-emergence to the emergence stage, in salt-stressed plants. In salt-stressed seedlings, greater numbers of LR primordia exhibit expression of a reporter gene driven by the auxin-sensitive DR5 promoter than in unstressed seedlings. Moreover, in the auxin transporter mutant aux1-7, the LR proliferation component of the salt SIMR is completely abrogated. The results suggest that salt stress promotes auxin accumulation in developing primordia thereby preventing their developmental arrest at the pre-emergence stage. Examination of ABA and ethylene mutants revealed that ABA synthesis and a factor involved in the ethylene signalling network also regulate the LR proliferation component of the salt SIMR.
植物根系在应对局部土壤条件时表现出显著的发育可塑性。本文表明，轻度盐胁迫会刺激拟南芥根系产生应激诱导形态发生反应（SIMR），这一反应类似于其他几种非生物胁迫：侧根（LR）的增殖，同时伴随着 LR 和主根长度的减少。将幼苗从低硝酸盐培养基转移到高硝酸盐培养基中，可显著增强盐 SIMR 的 LR 增殖成分，从而弥补 LR 长度的减少，维持整体 LR 表面积。LR 增殖是盐胁迫特有的（单独的渗透胁迫没有刺激作用），这是由于在盐胁迫下，更多的 LR 原基从萌芽前阶段进展到萌芽阶段。在盐胁迫的幼苗中，比未受胁迫的幼苗中，更多的 LR 原基表达由生长素敏感的 DR5 启动子驱动的报告基因。此外，在生长素转运体突变体 aux1-7 中，盐 SIMR 的 LR 增殖成分完全被消除。结果表明，盐胁迫促进了发育原基中生长素的积累，从而防止了它们在萌芽前阶段的发育停滞。对 ABA 和乙烯突变体的研究表明，ABA 合成和参与乙烯信号网络的因子也调节盐 SIMR 的 LR 增殖成分。
