Desbrosses Guilhem, Contesto Céline, Varoquaux Fabrice, Galland Marc, Touraine Bruno
Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR113, Université Montpellier, 2/IRD/CIRAD/SupAgro/INRA, Université Montpellier 2, Montpellier, France.
Plant Signal Behav. 2009 Apr;4(4):321-3. doi: 10.4161/psb.4.4.8106.
Using their 1-amino cyclopropane-1-carboxylic acid (ACC) deaminase activity, many rhizobacteria can divert ACC from the ethylene biosynthesis pathway in plant roots. To investigate the role of this microbial activity in plant responses to plant growth-promoting rhizobacteria (PGPR), we analyzed the effects of knock-out and wild-type PGPR strains on two phenotypic responses to inoculation—root hair elongation and root system architecture—in . Our work shows that rhizobacterial AcdS activity has a negative effect on root hair elongation, as expected from the reduction of ethylene production rate in root cells, while it has no impact on root system architecture. This suggests that PGPR triggered root hair elongation is independent of ethylene biosynthesis or signaling pathway. In addition, it does indicate that AcdS activity alters local regulatory processes, but not systemic regulations such as those that control root architecture. Our work also indicates that root hair elongation induced by PGPR inoculation is probably an auxin-independent mechanism. These findings were unexpected since genetic screens for abnormal root hair development mutants led to the isolation of ethylene and auxin mutants. Our work hence shows that studying the interaction between a PGPR and the model plant Arabidopsis is a useful system to uncover new pathways involved in plant plasticity.
许多根际细菌利用其1-氨基环丙烷-1-羧酸（ACC）脱氨酶活性，可使植物根中的ACC从乙烯生物合成途径中分流出来。为了研究这种微生物活性在植物对促植物生长根际细菌（PGPR）反应中的作用，我们分析了基因敲除型和野生型PGPR菌株对拟南芥接种后的两种表型反应——根毛伸长和根系结构的影响。我们的研究表明，根际细菌的AcdS活性对根毛伸长有负面影响，这正如根细胞中乙烯产生速率降低所预期的那样，而对根系结构没有影响。这表明PGPR引发的根毛伸长与乙烯生物合成或信号传导途径无关。此外，这确实表明AcdS活性改变了局部调节过程，但没有改变诸如控制根系结构的系统调节。我们的研究还表明，PGPR接种诱导的根毛伸长可能是一种不依赖生长素的机制。这些发现出乎意料，因为对根毛发育异常突变体的遗传筛选导致分离出乙烯和生长素突变体。因此，我们的研究表明，研究PGPR与模式植物拟南芥之间的相互作用是揭示植物可塑性所涉及新途径的有用系统。
