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甘蔗(Saccharum species hybrid)是最重要的糖料作物,由于其生育周期长,生物量大,对钾的需求量也大。南方是我国甘蔗的主要种植区域,由于土壤本身特性,有效钾含量低,限制了甘蔗的生产。因此,培育耐低钾甘蔗品种是提高甘蔗钾吸收效率的有效途径之一。本研究以甘蔗品种新台糖22号为材料进行低钾胁迫处理,利用RT-PCR技术从其根系中克隆得到钾转运蛋白基因,命名为SsHAK2(Gen Bank登录号:KM98738)。该基因全长为2 798 bp,包含一个完整的2 352 bp的ORF,编码784个氨基酸,相对分子量为87.602 k D,等电点为8.85,预测其为碱性蛋白。SsHAK2苷酸序列包含了12个跨膜结构域(S1~S12),有80%的概率定位在细胞质膜上。同时,该基因还包含3个保守结构域,分别为钾转运蛋白结构域和氨基酸转运蛋白结构域。SsHAK2基因与玉米(Zea mays)、大麦(Hordeum vulgare)、水稻(Oryza sativa)等其他作物中HAK基因具有高度的同源性,一致的核苷酸比例在52%~95%。q PCR分析结果表明,在低钾、干旱和盐胁迫下,SsHAK2的表达都发生改变。在低钾胁迫条件下处理96 h,该基因相对表达量最大,约达到对照的1.70倍;在盐胁迫条件下处理48 h,该基因的相对表达量出现显著上调,96 h相对表达量最高,约为对照的4.37倍。在干旱胁迫12 h,该基因的相对表达量达到最高,约为对照的4.07倍。干旱胁迫处理24 h,该基因表达量约为对照的1.69倍。但是,在干旱胁迫24到48 h过程中表达由下调转为上调。干旱胁迫48 h后,该基因的表达迅速下调,96 h时该基因表达量最低,约为对照表达量的1/4。q PCR分析结果表明该基因在低钾、干旱和盐胁迫下发挥重要的调控作用。本研究结果为进一步研究甘蔗钾吸收分子机制提供基础。
Saccharum species hybrid is the most important sugarcane crop, due to its long growth period, large biomass and large potassium demand. The south is the main planting area for sugar cane in our country. Due to the characteristics of the soil itself, the available potassium content is low, which limits the production of sugar cane. Therefore, cultivating low-K tolerant sugarcane varieties is one of the effective ways to improve the efficiency of sugarcane potassium absorption. In this study, the sugar cane Xintaishu 22 was treated with low potassium stress. The potassium transporter gene was cloned from its roots by RT-PCR and named as SsHAK2 (Gen Bank Accession No. KM98738). The full-length cDNA was 2 798 bp in length and contained a complete ORF of 2 352 bp encoding a protein of 784 amino acids with a relative molecular mass of 87.602 kD and an isoelectric point of 8.85. The SsHAK2 nucleotide sequence contains 12 transmembrane domains (S1-S12) with a 80% probability of localization on the plasma membrane. At the same time, the gene also contains three conserved domains, namely the potassium transporter domain and the amino acid transporter domain. The SsHAK2 gene has high homology with the HAK genes in other crops such as Zea mays, Hordeum vulgare and Oryza sativa, with consistent nucleotide ratios ranging from 52% to 95%. q PCR analysis showed that the expression of SsHAK2 changed under low potassium, drought and salt stress. Under low potassium stress for 96 h, the relative expression level of this gene was the highest, about 1.70 times of that of the control. Under salt stress conditions for 48 h, the relative expression of the gene was significantly up-regulated, About 4.37 times the control. At 12 h of drought stress, the relative expression of this gene reached the highest level, about 4.07 times that of the control. Drought stress treatment 24 h, the gene expression of about 1.69 times the control. However, the expression turned from down to up during the 24-48 h drought stress. After 48 h of drought stress, the gene expression was rapidly down-regulated and reached the lowest at 96 h, which was about 1/4 of the control. qPCR analysis showed that the gene plays an important regulatory role under low potassium, drought and salt stress. The results of this study provide the basis for further research on molecular mechanism of potassium catabolism.