Negi Sanjana, Tak Himanshu, Ganapathi T R
Plant Cell Culture Technology Section, Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
Transgenic Res. 2015 Jun;24(3):571-85. doi: 10.1007/s11248-014-9860-6. Epub 2014 Dec 19.
Vascular related NAC (NAM, ATAF and CUC) domain-containing genes regulate secondary wall deposition and differentiation of xylem vessel elements. MusaVND1 is an ortholog of Arabidopsis VND1 and contains the highly conserved NAC domain. The expression of MusaVND1 is highest in developing corm and during lignification conditions, the increase in expression of MusaVND1 coincides with the expression of PAL, COMT and C4H genes. MusaVND1 encodes a nuclear localized protein as MusaVND1-GFP fusion protein gets localized to nucleus. Transient overexpression of MusaVND1 converts banana embryogenic cells to xylem vessel elements, with a final differentiation frequency of 33.54% at the end of tenth day. Transgenic banana plants overexpressing MusaVND1 showed stunted growth and were characterized by PCR and Southern blot analysis. Transgenic banana plants showed transdifferentiation of various types of cells into xylem vessel elements and ectopic deposition of lignin in cells of various plant organs such as leaf and corm. Tracheary element formation was seen in the cortical region of transgenic corm as well as in epidermal cells of leaves. Biochemical analysis indicates significantly higher levels of lignin and cellulose content in transgenic banana lines than control plants. MusaVND1 overexpressing transgenic banana plants showed elevated expression levels of genes involved in lignin and cellulose biosynthesis pathway. Further expression of different MYB transcription factors positively regulating secondary wall deposition was also up regulated in MusaVND1 transgenic lines.
与血管相关的含NAC（NAM、ATAF和CUC）结构域的基因调控木质部导管分子的次生壁沉积和分化。香蕉VND1是拟南芥VND1的直系同源基因，含有高度保守的NAC结构域。香蕉VND1在发育中的球茎中表达最高，在木质化条件下，香蕉VND1表达的增加与苯丙氨酸解氨酶（PAL）、咖啡酸-O-甲基转移酶（COMT）和肉桂酸-4-羟化酶（C4H）基因的表达一致。香蕉VND1编码一种定位于细胞核的蛋白质，因为香蕉VND1-绿色荧光蛋白（GFP）融合蛋白定位于细胞核。香蕉VND1的瞬时过表达将香蕉胚性细胞转化为木质部导管分子，在第十天结束时最终分化频率为33.54%。过表达香蕉VND1的转基因香蕉植株生长受阻，并通过聚合酶链反应（PCR）和Southern杂交分析进行表征。转基因香蕉植株显示出各种类型的细胞转分化为木质部导管分子，并且在叶和球茎等各种植物器官的细胞中木质素异位沉积。在转基因球茎的皮层区域以及叶片的表皮细胞中可见管状分子形成。生化分析表明，转基因香蕉株系中木质素和纤维素含量明显高于对照植株。过表达香蕉VND1的转基因香蕉植株显示出参与木质素和纤维素生物合成途径的基因表达水平升高。在香蕉VND1转基因株系中，正向调控次生壁沉积的不同MYB转录因子的进一步表达也上调。
