Genome-Wide Characterization of AspATs in Populus: Gene Expression Variation and Enzyme Activities in Response to Nitrogen Perturbations
Genome-Wide Characterization of AspATs in Populus: Gene Expression Variation and Enzyme Activities in Response to Nitrogen Perturbations
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杨属 AspAT 的全基因组表征：响应氮扰动的基因表达变异和酶活性
DOI：
10.3390/f10050449
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发表时间：
2019-05
期刊：
影响因子：
2.9
通讯作者：
Li Mingzhi
中科院分区：
文献类型：
--
作者：
Su Tao;Han Mei;Min Jie;Cao Dan;Zhai Guangqing;Zhou Huaiye;Li Nanyue;Li Mingzhi
天冬氨酸转氨酶（AspAT）催化谷氨酸和草酰乙酸之间的可逆转氨化反应，生成天冬氨酸和2-氧葡萄糖酸，在所有细胞生物的氨基酸生物合成和氮(N)和碳代谢的稳态中发挥主要作用。虽然AspAT的生化表征已经取得了几十年的进展，但AspAT基因家族不同成员的分子和生理特征仍然知之甚少，特别是在森林树木中。本研究对黑棉杨（Populus trichocarpa Torr）的AspAT编码基因进行了广泛的全基因组调查。& a . Gray)，木本植物的模式种。通过对杨树基因组系统发育、基因结构、染色体分布、顺式元件、保守基序和亚细胞靶向性的深入研究，鉴定出10个AspAT同基因（PtAspAT1-10）。RNA-seq和定量实时聚合酶链反应（qRT-PCR）验证显示，PtAspATs具有多种组织特异性表达模式。进一步分析了同源aspat在杨树杂交无性系“南林895”中的时空表达，发现同源aspat基因的表达随源库动态而变化。AspAT转录本对N饥饿和季节性衰老的影响表明，叶片中5种AspAT转录本上调，而根中6种或6种以上AspAT转录本急剧下调。此外，在N过量的情况下，在根中观察到更多的aspat转录本的显著减少。因此，通过凝胶内测定，AspAT活性在氮饥饿时被显著抑制，这促使人们认为酶活性是氮胁迫下生长形态的更直接指标。综上所述，胁迫提示下的表达谱和酶活性为揭示木本植物特定基因在氮获取和再动员调控中的生理意义提供了理论基础。
Aspartate aminotransferase (AspAT) catalyzes a reversible transamination reaction between glutamate and oxaloacetate to yield aspartate and 2-oxoglutarate, exerting a primary role in amino acid biosynthesis and homeostasis of nitrogen (N) and carbon metabolism within all cellular organisms. While progress in biochemical characterization of AspAT has been made for decades, the molecular and physiological characteristics of different members of the AspAT gene family remain poorly known particularly in forest trees. Here, extensive genome-wide survey of AspAT encoding genes was implemented in black cottonwood (Populus trichocarpa Torr. & A. Gray), a model species of woody plants. Thorough inspection of the phylogenies, gene structures, chromosomal distribution, cis-elements, conserved motifs, and subcellular targeting resulted in the identification of 10 AspAT isogenes (PtAspAT1-10) in the Populus genome. RNA-seq along with quantitative real-time polymerase chain reaction (qRT-PCR) validation revealed that PtAspATs displayed diverse patterns of tissue-specific expression. Spatiotemporal expressions of homologous AspATs in the poplar hybrid clone Nanlin895' were further evaluated, showing that gene expressions varied depending on source-sink dynamics. The impact on AspAT transcripts upon N starvation and seasonal senescence showed the upregulation of five AspAT in leaves concurrent with drastic downregulation of six or more AspATs in roots. Additionally, marked reductions of many more AspATs transcripts were observed in roots upon N excess. Accordingly, AspAT activities were significantly suppressed upon N starvation by an in-gel assay, prompting the argument that enzyme activity was a more direct indicator of the growth morphology under a N stress regime. Taken together, the expression profiling and enzyme activities upon stress cues provide a theoretical basis for unraveling the physiological significance of specific gene(s) in regulation of N acquisition and remobilization in woody plants.
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