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Abstract：
Although Al3+-toxicity is one of the limiting factors for crop production in acidic soils, little is known about the Al3+-tolerance mechanism in watermelon, a fairly acid-tolerant crop. This work aimed to identify the interaction between the H2O2 scavenging pathway and auxin glycosylation relevant to watermelon Al3+-tolerance. By analyzing expressions of hormone-related ClUGTs and antioxidant enzyme genes in Al3+-tolerant (ZJ) and Al3+-sensitive (NBT) cultivars, we identified ClUGT75s (B1, B2, and D1) and ClSOD1-2-ClCAT as crucial components associated with Al3+-tolerance. Al3+-stress significantly increased H2O2 content by 92.7% in NBT and 42.3% in ZJ, accompanied by less Al3+-, auxin (IAA and IBA), and MDA contents in ZJ than NBT. These findings coincided with significant ClSOD1-2 expression and stable dismutation activity in NBT than ZJ. Hence, higher H2O2 content in the root apex of NBT than ZJ correlated with a significant increase in auxin content and ClSOD1-2 up-regulation. Moreover, Al3+-activated ClUGT75D1 and ClUGT75B2 in ZJ coincided with no considerable change in IBA content, suggesting that glycosylation-mediated changes in IBA content might be relevant to Al3+-tolerance in watermelon. Furthermore, exogenous H2O2 and IBA indicated ClUGT75D1 modulating IBA is likely dependent on H2O2 background. We hypothesize that a higher H2O2 level in NBT represses ClUGT75, resulting in increased auxin than those in ZJ roots. Thus, excess in both H2O2 and auxin aggravated the inhibition of root elongation under Al3+-stress. Our findings provide insights on the permissive action of H2O2 in the mediation of auxin glycosylation by ClUGT75 in root apex for Al3+-tolerance in watermelon.
摘要：
尽管Al3毒性是酸性土壤中作物生产的限制因素之一，对西瓜的Al3+耐受机制知之甚少，一种相当耐酸的作物。这项工作旨在确定H2O2清除途径与西瓜Al3耐受性相关的生长素糖基化之间的相互作用。通过分析耐Al3（ZJ）和Al3敏感（NBT）品种中激素相关ClUGTs和抗氧化酶基因的表达，我们确定了ClUGT75s（B1，B2和D1）和ClSOD1-2-ClCAT是与Al3耐受性相关的关键成分。Al3+胁迫显著增加NBT中H2O2含量92.7%,ZJ中H2O2含量42.3%,伴随着较少的Al3+-，生长素（IAA和IBA），ZJ中MDA含量高于NBT。这些发现与NBT中显着的ClSOD1-2表达和稳定的歧化活性比ZJ相吻合。因此，NBT根尖中H2O2含量高于ZJ，与生长素含量显着增加和ClSOD1-2上调相关。此外，ZJ中Al3+激活的ClUGT75D1和ClUGT75B2一致，IBA含量没有显著变化，表明糖基化介导的IBA含量变化可能与西瓜的Al3耐受性有关。此外，外源H2O2和IBA表明ClUGT75D1调节IBA可能依赖于H2O2背景。我们假设NBT中较高的H2O2水平抑制ClUGT75，导致生长素比ZJ根中的生长素增加。因此，在Al3胁迫下，H2O2和生长素的过量会加剧根伸长的抑制。我们的发现提供了有关H2O2在西瓜根尖中通过ClUGT75介导生长素糖基化介导Al3耐受性的许可作用的见解。
