Nitrogenase activity and trehalose content of nodules of drought-stressed common beans infected with effective (Fix+) and ineffective (Fix-) rhizobia
2004
Jimenez Zacarias, J.J. | Altamirano-Hernandez, J. | Pena Cabriales, J.J.
Nitrogenase activity and trehalose accumulation were measured in nodulated and non-nodulated common beans (Phaseolus vulgaris) that were exposed to drought. Plants were infected with the Fix(+) Rhizobiumsp NGR234, or a Fix(-) derivative (NGRomegafixF), or high trehalose-producing, native rhizobia. Trehalose content increased significantly while acetylene reduction activity (ARA) decreased in the nodules of plants exposed to drought. Nevertheless, ARA decreased at a slower rate in nodules with high trehalose levels. Under water stress, nodules infected with NGRomegafixF tended to accumulate more trehalose than nodules infected with wild-type NGR234 (9 +/- 0.1 vs 8 +/- 0.1 mg g(-1) dw. respectively). Highest trehalose accumulations were registered in nodules of plants infected with native rhizobia (average 16 mg g(-1) dw), and these plants also exhibited the highest relative water content (65%), while in plants infected with the NGRomegafixF RWC was significantly lower (56%). Our results suggest that nodule trehalose may protect bacterial nitrogenase activity under drought conditions, and that both trehalose and biological nitrogen fixation (BNF) contribute to drought tolerance.
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