School of Earth and Environment, the University of Western Australia, Crawley WA 6009, Australia.
J Exp Bot. 2010 Jun;61(11):3163-75. doi: 10.1093/jxb/erq143. Epub 2010 May 23.
Aluminium (Al) rhizotoxicity coincides with low pH; however, it is unclear whether plant tolerance to these two factors is controlled by the same mechanism. To address this question, the Al-resistant alr104 mutant, two Al-sensitive mutants (als3 and als5), and wild-type Arabidopsis thaliana were compared in long-term exposure (solution culture) and in short-term exposure experiments (H(+) and K(+) fluxes, rhizosphere pH, and plasma membrane potential, E(m)). Based on biomass accumulation, als5 and alr104 showed tolerance to low pH, whereas alr104 was tolerant to the combined low-pH/Al treatment. The sensitivity of the als5 and als3 mutants to the Al stress was similar. The Al-induced decrease in H(+) influx at the distal elongation zone (DEZ) and Al-induced H(+) efflux at the mature zone (MZ) were higher in the Al-sensitive mutants (als3 and als5) than in the wild type and the alr104 mutant. Under combined low-pH/Al treatment, alr104 and the wild type had depolarized plasma membranes for the entire 30 min measurement period, whereas in the Al-sensitive mutants (als3 and als5), initial depolarization to around -60 mV became hyperpolarization at -110 mV after 20 min. At the DEZ, the E(m) changes corresponded to the changes in K(+) flux: K(+) efflux was higher in alr104 and the wild type than in the als3 and als5 mutants. In conclusion, Al tolerance in the alr104 mutant correlated with E(m) depolarization, higher K(+) efflux, and higher H(+) influx, which led to a more alkaline rhizosphere under the combined low-pH/Al stress. Low-pH tolerance (als5) was linked to higher H(+) uptake under low-pH stress, which was abolished by Al exposure.
铝（Al）的根系毒性与低 pH 值有关；然而，尚不清楚植物对这两个因素的耐受性是否受同一机制控制。为了解决这个问题，我们比较了耐铝 alr104 突变体、两个铝敏感突变体（als3 和 als5）和野生型拟南芥在长期暴露（溶液培养）和短期暴露实验（H(+)和 K(+)通量、根际 pH 值和质膜电位，E(m)）中的表现。基于生物量积累，als5 和 alr104 对低 pH 值表现出耐受性，而 alr104 对低 pH 值/Al 联合处理具有耐受性。als5 和 als3 突变体对 Al 胁迫的敏感性相似。在远端伸长区（DEZ）中，Al 诱导的 H(+)内流减少和在成熟区（MZ）中，Al 诱导的 H(+)外排在铝敏感突变体（als3 和 als5）中比野生型和 alr104 突变体更高。在低 pH 值/Al 联合处理下，alr104 和野生型在整个 30 分钟测量期间质膜去极化，而在铝敏感突变体（als3 和 als5）中，初始去极化至约-60 mV 在 20 分钟后变为超极化。在 DEZ 处，E(m)变化与 K(+)通量变化相对应：在 alr104 和野生型中，K(+)外排高于 als3 和 als5 突变体。总之，alr104 突变体中的 Al 耐受性与 E(m)去极化、更高的 K(+)外排和更高的 H(+)内流相关，这导致在低 pH 值/Al 联合胁迫下根际更碱性。低 pH 值耐受性（als5）与低 pH 值胁迫下更高的 H(+)摄取有关，而 Al 暴露会消除这种摄取。
