Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, USA.
Planta. 2023 Sep 18;258(4):82. doi: 10.1007/s00425-023-04235-8.
Transgenic overexpression of a NtEGY2 gene restores normal green color of burley tobacco plants, but does not increase nitrogen utilization efficiency beyond that exhibited by wild-type individuals. Nitrogen physiology is important in tobacco because of its role in generation of leaf yield and accumulation of nitrogen-containing alkaloids that can react with nitrosating agents in the formation of carcinogenic tobacco-specific nitrosamines. Cultivars of the burley tobacco market class are homozygous for deleterious mutant alleles at the duplicate Yb and Yb loci which have previously been associated with decreased nitrogen use and utilization efficiency; increased leaf nitrate, total nitrogen, and alkaloid levels; and reduced yields. How mutant alleles at these two loci affect these traits is not well understood. Recent characterization of the Yb and Yb genes (homologs of Arabidopsis EGY1 gene) enabled overexpression of the wild-type Yb allele in ybybybyb plants to determine if observed unfavorable effects were due to linkage or pleiotropy, and to determine if overexpression could lead to beneficial modifications in any of these traits in transgenic plants relative to naturally-occurring wild-type genotypes. Yb overexpression was found to confer an agronomic benefit to ybybybyb genotypes but no advantage to wild-type genotypes. RNA-Seq was used to carry out a comparative transcriptome analysis of genetically engineered and wild-type nearly isogenic lines (NILs) to gain insight on metabolic pathways affecting carbon and nitrogen metabolism that might be altered as the result of genetic variability at the Yb and Yb loci. Results indicate that complex changes in the transcriptome of tobacco can be manifested by altered expression of Yb.
转 NtEGY2 基因过量表达使白肋烟植株恢复正常绿色，但氮素利用效率并未超过野生型个体。氮素生理学在烟草中很重要，因为它在叶片产量的产生和含氮生物碱的积累中起作用，而含氮生物碱可以与亚硝化剂反应，形成致癌的烟草特异性亚硝胺。白肋烟市场品种类是 Yb 和 Yb 位点的有害突变等位基因的纯合子，这些突变等位基因先前与氮素利用和利用效率降低、叶片硝酸盐、总氮和生物碱水平增加以及产量降低有关。这两个位点的突变等位基因如何影响这些性状还不太清楚。最近对 Yb 和 Yb 基因（拟南芥 EGY1 基因的同源物）的特征描述，使 Yb 等位基因在 ybybybyb 植株中的野生型过表达成为可能，以确定观察到的不利影响是由于连锁还是多效性引起的，以及确定过表达是否会导致转基因植物相对于自然发生的野生型基因型在任何这些性状中产生有益的修饰。发现 Yb 过表达赋予了 ybybybyb 基因型一个农艺优势，但对野生型基因型没有优势。RNA-Seq 被用于对遗传工程和野生型近等基因系（NILs）进行比较转录组分析，以深入了解影响碳和氮代谢的代谢途径，这些途径可能由于 Yb 和 Yb 位点的遗传变异而发生改变。结果表明，Yb 的表达改变可能导致烟草转录组的复杂变化。
