Overexpression of the sucrose transporter gene NtSUT1 alleviates aluminum-induced inhibition of root elongation in tobacco (Nicotiana tabacum L.)
Overexpression of the sucrose transporter gene NtSUT1 alleviates aluminum-induced inhibition of root elongation in tobacco (Nicotiana tabacum L.)
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DOI：
10.1080/00380768.2017.1283646
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发表时间：
2017-01
影响因子：
2
通讯作者：
Koki Kariya;M. Sameeullah;Takayuki Sasaki;Yoko Yamamoto
中科院分区：
文献类型：
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作者：
Koki Kariya;M. Sameeullah;Takayuki Sasaki;Yoko Yamamoto
摘要研究质膜定位蔗糖/H+同向转运体基因（NtSUT 1）在烟草根伸长生长中的作用。CV. Samsun NN）在铝（Al）胁迫下的抗性，通过构建的NtSUT 1过表达（OX）和抑制（RNAi）系与野生型（WT）烟草的比较研究，发现NtSUT 1的过表达或抑制受花椰菜花叶病毒35 S启动子控制。使每个品系的幼苗在不含或含氯化铝（AlCl 3）的营养培养基（pH 4.5）中生长。分析根以确定根伸长的程度和NtSUT 1的转录水平、可溶性糖含量和根尖细胞存活。与野生型相比，OX和RNAi株系根尖可溶性糖含量分别升高和降低。在16小时光照/8小时黑暗光周期和不存在Al的情况下，OX和WT的根伸长速率相似，但RNAi显著降低。在Al的存在下，铝诱导的根伸长抑制程度在OX中较低，而在RNAi中高于WT。在根尖，在24小时铝处理的细胞死亡的启动在OX和加速RNAi，在WT相比，减速。24小时铝处理后，根尖处剩余的活细胞数在OX中高于WT，在RNAi中低于WT。在黑暗中，根的生长是由培养基中提供的蔗糖作为光合同化物的替代物支持的。在铝胁迫下，NtSUT 1的转录水平与根尖可溶性糖含量和根伸长速率之间均呈显著正相关。总之，这些结果表明，NtSUT 1在根尖主要支持蔗糖吸收通过质外体途径，蔗糖积极影响根伸长。我们的结论是，在根尖NtSUT 1的过表达增加可溶性糖含量，导致更大的细胞存活和根伸长铝胁迫下，导致铝耐性表型。
ABSTRACT We aimed to investigate the role of the plasma membrane-localized sucrose/H+ symporter gene (NtSUT1) in root elongation growth of tobacco seedlings (Nicotiana tabacum L. cv. Samsun NN) under aluminum (Al) stress, by comparative study between wild-type (WT) tobacco and constructed over-expression (OX) and suppression (RNAi) lines of NtSUT1, in which the overexpression or suppression of NtSUT1 was controlled by the cauliflower mosaic virus 35S promoter. Seedlings of each line were grown in a nutrient medium (pH 4.5) without or with aluminum chloride (AlCl3). The roots were analyzed to determine the degree of root elongation and the transcript levels of NtSUT1, soluble sugar content, and cell survival at the root apex. The transcript level of NtSUT1 at the root apex was negatively affected by Al. Compared with WT, OX lines and RNAi lines had higher and lower contents of soluble sugars at the root apex, respectively. Under a 16-h light/8-h dark photoperiod and in the absence of Al, the root elongation rate was similar in OX and WT, but was significantly decreased in RNAi. In the presence of Al, the degree of Al-induced inhibition of root elongation was lower in OX and higher in RNAi than in WT. At the root apex, the initiation of cell death during a 24-h Al treatment was decelerated in OX and accelerated in RNAi, compared with that in WT. The number of live cells remaining at the root apex after the 24-h Al treatment was higher in OX and lower in RNAi than in WT. In the dark, root growth was supported by sucrose supplied in the medium as a substitute for photoassimilate. Under these conditions in the absence or presence of Al, there were strong positive correlations between the transcript level of NtSUT1, the soluble sugar content at the root apex and the root elongation rate. Together, these results indicate that NtSUT1 at the root apex primarily supports sucrose uptake via the apoplastic pathway, and that sucrose positively affects root elongation. We conclude that overexpression of NtSUT1 at the root apex increases the soluble sugar content, resulting in greater cell survival and root elongation under Al stress, leading to the Al-tolerance phenotype.