The Plant Cell:中科院遗传发育所植物NAD补救合成途径解析和进化研

摘要 : NAD (尼克酰胺腺嘌呤二核苷酸) 作为电子传递载体(辅酶)参与众多的氧化还原反应而为广大研究人员所熟知。

NAD (尼克酰胺腺嘌呤二核苷酸) 作为电子传递载体(辅酶)参与众多的氧化还原反应而为广大研究人员所熟知。在植物NAD补救合成途径中，都存在尼克酸(nicotinate，NA)和多种NA的衍生物(糖基化，甲基化等)，但迄今为止，关于NA衍生物在植物代谢中的分子机制及其生理功能尚未有报道。

中国科学院遗传与发育生物学研究所王国栋研究组首先利用色质联用技术发现拟南芥中NA的糖基化修饰发生在NA的N-位或者O-位，并且O-位糖基化分布呈现十字花科特异性。进一步利用基因表达-酶活关联分析，在糖基转移酶家族1中(共有106个成员)发现并功能鉴定三个NA糖基转移酶，包括一个NAOGT(UGT74F2，之前报道是水杨酸糖基转移酶)和两个NANGT(UGT76C4和UGT76C5)。拟南芥UGT74F2的突变体(ugt74f2-1)比野生型积累更高浓度的游离NA，这与ugt74f2-1在各种逆境条件下的种子萌发率呈负相关，同时ugt74f2-1种子萌发率下降与水杨酸的积累无关;过表达UGT74F2能够完全互补ugt74f2-1的种子萌发缺陷。这些发现结合全面的化学分析表明，NA的O-位糖基化修饰可能保护植物细胞免受种子萌发过程中NA过度积累所造成的毒害。综合NAD补救合成途径参与基因的进化树分析，结果表明NAOGT活性是在十字花科植物进化过程中才逐渐获得，NAOGT活性的获得为植物适应环境提供选择优势。该研究同时为进一步研究植物中其它NA衍生物的生物学功能奠定了基础。

该研究成果于6月26日在线发表于The Plant Cell(DOI：10.1105/tpc.15.00223)上。王国栋研究组的博士生李伟为该文章的第一作者。

十字花科新进化获得的NAOGT保护非生物逆境条件下的种子萌发

原文链接:

Nicotinate O-Glucosylation Is an evolutionarily Metabolic Trait Important for Seed Germination under Stress Conditions in Arabidopsis thaliana

原文摘要：

he glycosylation of nicotinate (NA), a key intermediate of the NAD salvage pathway, occurs widely in land plants. However, the physiological function of NAglycosylation is not well understood in planta, and no gene encoding NAglycosyltransferase has been reported to date. NA glycosylation in Arabidopsis thaliana occurs at either the N- or the O-position of the NA molecule, and O-glucosylation appears to be unique to the Brassicaceae. Using gene-enzyme correlations focused on Family 1 glycosyltransferases (GTs; EC 2.4), we identified and characterized three Arabidopsis GTs, which are likely involved in NAglycosylation. These include one NAOGT (UGT74F2; previously identified as a salicylic acid glycosyltransferases) and two NANGTs (UGT76C4 and UGT76C5). Arabidopsis mutants of UGT74F2 accumulate higher levels of free NA, but not salicylic acid, than that of the wild type, and this inversely correlated with seed germination rates under various abiotic stresses. The germination defect of theugt74f2-1 mutant could be fully complemented by overexpression of UGT74F2. These observations, together with comprehensive chemical analysis, suggest thatNA glycosylation may function to protect plant cells from the toxicity of NAoveraccumulation during seed germination. Combined with phylogenetic analysis, our results suggest that NAOGTs arose recently in the Brassicaceae family and may provide a fitness benefit. The multifunctionality of UGT74F2 in Arabidopsis is also investigated and discussed.

doi:10.1105/tpc.15.00223

作者：王国栋

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