Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.
Physiol Plant. 2013 Aug;148(4):502-11. doi: 10.1111/ppl.12005. Epub 2012 Dec 12.
The negative charges of cell wall pectin molecules attributed by pectin methylesterase (PME, EC 3.1.1.11) contribute to Al binding capacity. We examined the expression profiles of 35 members of the PME gene family in the root apex of an Al-sensitive rice 'Zhefu802' under Al stress. While root elongation was inhibited by 40% after 3-h exposure to 25 µM Al, cell wall PME activity and the abundance of eight PME genes transcripts were increased. The same Al treatment which had almost no effect on root elongation of an Al-resistant rice ssp. japonica 'Nipponbare' did not change the expression patterns of these eight PME genes. However, when Al concentration was increased to 50 µM, by which the root elongation of 'Nipponbare' was inhibited by 40% too, the expression of these PME genes were also upregulated except two genes with no signal. These suggest a possible correlation between the upregulated genes and Al-induced inhibition of root elongation in rice. Furthermore, these eight PME genes behaved differently when subjected to CdCl2 and LaCl3 treatments, implying the specificity of different PME genes in response to different metal toxicities. The transgenic rice overexpressing one of these eight PME genes OsPME14 showed higher PME activity and Al content in root tip cell wall, and became more sensitive to Al stress, verifying the involvement of the specific PME gene in Al toxicity. Therefore, our results provided the molecular evidence to connect the expression of specific PME genes with the Al-induced inhibition of root elongation in rice.
果胶甲酯酶（PME，EC 3.1.1.11）赋予细胞壁果胶分子的负电荷有助于 Al 结合能力。我们在 Al 敏感水稻‘Zhefu802’根尖中检查了 35 个 PME 基因家族成员在 Al 胁迫下的表达谱。在暴露于 25 µM Al 3 小时后，根伸长受到 40%的抑制，而细胞壁 PME 活性和 8 个 PME 基因转录本的丰度增加。同样的 Al 处理对 Al 抗性水稻亚种‘Nipponbare’的根伸长几乎没有影响，没有改变这 8 个 PME 基因的表达模式。然而，当 Al 浓度增加到 50 µM 时，‘Nipponbare’的根伸长也受到 40%的抑制，除了两个没有信号的基因外，这些 PME 基因的表达也上调了。这表明这些上调的基因与水稻中 Al 诱导的根伸长抑制之间可能存在相关性。此外，当这些 8 个 PME 基因受到 CdCl2 和 LaCl3 处理时，它们的表现不同，这表明不同的 PME 基因对不同金属毒性的特异性。过表达这 8 个 PME 基因之一 OsPME14 的转基因水稻表现出更高的 PME 活性和根尖细胞壁中的 Al 含量，对 Al 胁迫更敏感，验证了特定 PME 基因在 Al 毒性中的参与。因此，我们的结果为连接特定 PME 基因的表达与水稻中 Al 诱导的根伸长抑制提供了分子证据。
