TRICHOME BIREFRINGENCE-LIKE27 Affects Aluminum Sensitivity by Modulating the O-Acetylation of Xyloglucan and Aluminum-Binding Capacity in Arabidopsis

Xyloglucan (XyG) has been reported to contribute to the aluminum (Al)-binding capacity of the cell wall in Arabidopsis (Arabidopsis thaliana). However, the influence of O-acetylation of XyG, accomplished by the putative O-acetyltransferase TRICHOME BIREFRINGENCE-LIKE27 (TBL27 [AXY4]), on its Al-binding capacity is not known. In this study, we found that the two corresponding TBL27 mutants, axy4-1 and axy4-3, were more Al sensitive than wild-type Columbia-0 plants. TBL27 was expressed in roots as well as in leaves, stems, flowers, and siliques. Upon Al treatment, even within 30 min, TBL27 transcript accumulation was strongly down-regulated. The mutants axy4-1 and axy4-3 accumulated significantly more Al in the root and wall, which could not be correlated with pectin content or pectin methylesterase activity, as no difference in the mutants was observed compared with the wild type when exposed to Al stress. The increased Al accumulation in the wall of the mutants was found to be in the hemicellulose fraction. While the total sugar content of the hemicellulose fraction did not change, the O-acetylation level of XyG was reduced by Al treatment. Taken together, we conclude that modulation of the O-acetylation level of XyG influences the Al sensitivity in Arabidopsis by affecting the Al-binding capacity in the hemicellulose.

据报道，木糖葡萄糖（XYG）有助于拟南芥（拟南芥）中细胞壁的铝（Al）结合能力。然而，通过推定的O-乙酰基转移酶毛状体毛状类样（TBL27 [axy4]）对XYG的O-乙酰化的影响，对其AL结合能力的影响尚不清楚。在这项研究中，我们发现两个相应的TBL27突变体Axy4-1和Axy4-3比野生型哥伦比亚-0植物更敏感。 TBL27在根，茎，花和硅胶中表达。治疗后，即使在30分钟内，TBL27转录本的积累也被强烈下调。突变体Axy4-1和Axy4-3在根和壁上积累了更大的Al，这与果胶含量或果胶甲基酯酶活性无关，因为与野生型相比，突变体在暴露于Al胁迫时没有观察到突变体的差异。发现突变体壁中的Al积聚增加在半纤维素的部分中。尽管半纤维素级分的总糖含量没有变化，但通过Al处理，XYG的O-乙酰化水平降低。综上所述，我们得出的结论是，XYG的O-乙酰化水平的调节通过影响半纤维素的AL结合能力来影响拟南芥的Al敏感性。