Melo Janaina O, Lana Ubiraci G P, Piñeros Miguel A, Alves Vera M C, Guimarães Claudia T, Liu Jiping, Zheng Yi, Zhong Silin, Fei Zhangjun, Maron Lyza G, Schaffert Robert E, Kochian Leon V, Magalhaes Jurandir V
Embrapa Maize and Sorghum, Road. MG 424, km 65, 35701-970, Sete Lagoas, Minas Gerais, Brazil.
Departamento de Biologia Geral, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, 31270-901, Belo Horizonte, Minas Gerais, Brazil.
Plant J. 2013 Jan;73(2):276-88. doi: 10.1111/tpj.12029. Epub 2012 Nov 26.
Impaired root development caused by aluminum (Al) toxicity is a major cause of grain yield reduction in crops cultivated on acid soils, which are widespread worldwide. In sorghum, the major Al-tolerance locus, AltSB , is due to the function of SbMATE, which is an Al-activated root citrate transporter. Here we performed a molecular and physiological characterization of various AltSB donors and near-isogenic lines harboring various AltSB alleles. We observed a partial transfer of Al tolerance from the parents to the near-isogenic lines that was consistent across donor alleles, emphasizing the occurrence of strong genetic background effects related to AltSB . This reduction in tolerance was variable, with a 20% reduction being observed when highly Al-tolerant lines were the AltSB donors, and a reduction as great as 70% when other AltSB alleles were introgressed. This reduction in Al tolerance was closely correlated with a reduction in SbMATE expression in near-isogenic lines, suggesting incomplete transfer of loci acting in trans on SbMATE. Nevertheless, AltSB alleles from the highly Al-tolerant sources SC283 and SC566 were found to retain high SbMATE expression, presumably via elements present within or near the AltSB locus, resulting in significant transfer of the Al-tolerance phenotype to the derived near-isogenic lines. Allelic effects could not be explained by coding region polymorphisms, although occasional mutations may affect Al tolerance. Finally, we report on the extensive occurrence of alternative splicing for SbMATE, which may be an important component regulating SbMATE expression in sorghum by means of the nonsense-mediated RNA decay pathway.
铝（Al）毒性导致的根系发育受损是酸性土壤上种植的作物籽粒产量降低的主要原因，酸性土壤在全球广泛分布。在高粱中，主要的耐铝位点AltSB归因于SbMATE的功能，SbMATE是一种铝激活的根系柠檬酸转运蛋白。在这里，我们对携带各种AltSB等位基因的不同AltSB供体和近等基因系进行了分子和生理特征分析。我们观察到耐铝性从亲本部分转移到近等基因系，且这种转移在不同供体等位基因中是一致的，这强调了与AltSB相关的强大遗传背景效应的存在。这种耐受性的降低是可变的，当高耐铝系作为AltSB供体时，耐受性降低20%，而当其他AltSB等位基因渗入时，耐受性降低高达70%。耐铝性的这种降低与近等基因系中SbMATE表达的降低密切相关，这表明反式作用于SbMATE的位点转移不完全。然而，来自高耐铝源SC283和SC566的AltSB等位基因被发现保留了较高的SbMATE表达，推测是通过AltSB位点内或附近存在的元件，从而导致耐铝表型显著转移到衍生的近等基因系中。尽管偶尔的突变可能影响耐铝性，但等位基因效应无法通过编码区多态性来解释。最后，我们报道了SbMATE广泛存在可变剪接，这可能是通过无义介导的RNA降解途径调节高粱中SbMATE表达的一个重要组成部分。
