Functional conservation and divergence of Miscanthus lutarioriparius GT43 gene family in xylan biosynthesis.
Functional conservation and divergence of Miscanthus lutarioriparius GT43 gene family in xylan biosynthesis.
复制标题
芒草GT43基因家族在木聚糖生物合成中的功能保守性和分化
DOI：
10.1186/s12870-016-0793-5
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发表时间：
2016-04-26
影响因子：
5.3
通讯作者：
Zhou G
中科院分区：
文献类型：
--
作者：
Wang X;Tang Q;Zhao X;Jia C;Yang X;He G;Wu A;Kong Y;Hu R;Zhou G
木聚糖是植物细胞壁中含量最丰富的非纤维素多糖。在模式植物拟南芥中，木聚糖的生物合成已经取得了很大的进展。糖基转移酶(GT)家族43的两对同源的不规则木质部9(IRX9)/9L和IRX14/14L在木聚糖骨架的生物合成中起着关键作用。然而，在芒属等牧草中木聚糖的生物合成仍然知之甚少。我们在一种很有前途的生物能源作物--褐藻中鉴定了七个GT43成员。实时定量RT-PCR分析表明，M1GT43基因在被检测的组织中普遍存在表达。原位杂交结果表明，MlGT43A-B和MlGT43F-G在厚壁组织中特异表达，而MlGT43C-E在厚壁组织和薄壁组织中均有表达。7个M1GT43蛋白均定位于高尔基体。在irx9中过表达MlGT43A-E而不是MlGT43F和MlGT43G可以完全或部分挽救突变的缺陷，包括形态变化、木质部塌陷和木聚糖含量增加；而MlGT43F和MlGT43G的过表达补充了irx14的缺陷，表明MlGT43A-E是IRX9的功能同源，而MlGT43F和MlGT43G是IRX14的功能同源。然而，所有7个M1GT43基因的过表达都不能挽救irx14种子的粘液缺陷。此外，MlGT43A-E报告的瞬时转录激活分析表明，MlSND1、M1MYB46或MlVND7对MlGT43A和MlGT43B具有差异激活作用，而对MlGT43C-E没有激活作用。结果表明，在次生细胞壁形成过程中，7个M1GT43基因在木聚糖生物合成中功能保守，但在种皮粘液中木聚糖生物合成具有多样性。研究结果为进一步深入了解牧草中木聚糖的生物合成提供了依据，为进一步对牧草细胞壁成分和结构进行基因改造以更好地适应下一代生物燃料生产奠定了基础。
Xylan is the most abundant un-cellulosic polysaccharides of plant cell walls. Much progress in xylan biosynthesis has been gained in the model plant species Arabidopsis. Two homologous pairs Irregular Xylem 9 (IRX9)/9L and IRX14/14L from glycosyltransferase (GT) family 43 have been proved to play crucial roles in xylan backbone biosynthesis. However, xylan biosynthesis in grass such as Miscanthus remains poorly understood. We characterized seven GT43 members in M. lutarioriparius, a promising bioenergy crop. Quantitative real-time RT-PCR (qRT-PCR) analysis revealed that the expression of MlGT43 genes was ubiquitously detected in the tissues examined. In-situ hybridization demonstrated that MlGT43A-B and MlGT43F-G were specifically expressed in sclerenchyma, while MlGT43C-E were expressed in both sclerenchyma and parenchyma. All seven MlGT43 proteins were localized to Golgi apparatus. Overexpression of MlGT43A-E but not MlGT43F and MlGT43G in Arabidopsis irx9 fully or partially rescued the mutant defects, including morphological changes, collapsed xylem and increased xylan contents, whereas overexpression of MlGT43F and MlGT43G but not MlGT43A-E complemented the defects of irx14, indicating that MlGT43A-E are functional orthologues of IRX9, while MlGT43F and MlGT43G are functional orthologues of IRX14. However, overexpression of all seven MlGT43 genes could not rescue the mucilage defects of irx14 seeds. Furthermore, transient transactivation analyses of MlGT43A-E reporters demonstrated that MlGT43A and MlGT43B but not MlGT43C-E were differentially activated by MlSND1, MlMYB46 or MlVND7. The results demonstrated that all seven MlGT43s are functionally conserved in xylan biosynthesis during secondary cell wall formation but diversify in seed coat mucilage xylan biosynthesis. The results obtained provide deeper insight into xylan biosynthesis in grass, which lay the foundation for genetic modification of grass cell wall components and structure to better suit for next-generation biofuel production.