National Engineering Research Centre for Wheat, Henan Agricultural University, Zhengzhou 450002, China.
C R Biol. 2010 Oct;333(10):716-24. doi: 10.1016/j.crvi.2010.06.003. Epub 2010 Aug 23.
ADP-glucose pyrophosphorylase (AGPase), the key enzyme of starch synthesis in plants, is composed of two small and two large subunits, and has plastidial and cytosolic isoforms. In kernels of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), transcripts for cytosolic (Ta.AGP.S1a) and plastidial (Ta.AGP.S1b) small subunits of AGPase were encoded by the same gene (Ta.AGP.S.1) by use of the alternative first exons. In this study, a cDNA sequence (1631 bp) [NCBI: EU586278] encoding a novel Ta.AGP.S1b transcript was isolated in kernels of Chinese common wheat cultivars. Compared with another Ta.AGP.S1b transcript [NCBI: FJ643609] isolated in kernels of non-Chinese wheat cultivars, EU586278 lacked a long fragment (117 bp) at its 5'terminal, resulting in a shorten transit peptide. The lacked fragments of Ta.AGP.S1b (EU586278) were universally found in surveyed 22 Chinese common wheat cultivars. Partial genomic DNA sequence [NCBI: FJ907395] of Ta.AGP.S.1 gene, which was corresponded to 5'terminal of EU586278 transcript, was also isolated in Chinese common cultivars and sequencing indicated that FJ907395 contained the corresponding lacked fragment of EU586278 transcript, inferring the lacked fragment in EU586278 transcript was not present in the genome, but possibly occurred at transcription level. Using TargetP software, the predicated transit peptide of putative plastidial SSU encoded by EU586278 contained merely 25 amino acids, considerably shorter than those of other plant AGP. S.1bs (54-70 amino acids). Phylogenetic tree analysis indicated that the amino acid sequence of EU586278 transit peptide was not clustered together with those of other wheat Ta.AGP.S1bs [NCBI: AF536819 and FJ643609] and barley AGP.S1b [NCBI: Z48563]. These implied that EU586278 could be a novel Ta.AGP.S1b transcript. Semi-quantitative PCR analysis indicated that transcripts of EU586278 were abundantly expressed in leaf, moderately in endosperm and stem, and weakly in root.
ADP-葡萄糖焦磷酸化酶（AGPase）是植物中淀粉合成的关键酶，由两个小亚基和两个大亚基组成，具有质体和细胞质同工酶。在小麦（Triticum aestivum L.）和大麦（Hordeum vulgare L.）的籽粒中，AGPase 的细胞质（Ta.AGP.S1a）和质体（Ta.AGP.S1b）小亚基的转录本由同一基因（Ta.AGP.S.1）使用替代的第一个外显子编码。在这项研究中，从中国普通小麦品种的籽粒中分离到了一个编码新型 Ta.AGP.S1b 转录本的 cDNA 序列（1631bp）[NCBI：EU586278]。与在非中国小麦品种的籽粒中分离到的另一个 Ta.AGP.S1b 转录本[NCBI：FJ643609]相比，EU586278 在其 5'末端缺少一个长片段（117bp），导致转运肽缩短。在调查的 22 个中国普通小麦品种中，普遍发现 Ta.AGP.S1b（EU586278）的缺失片段。Ta.AGP.S.1 基因的部分基因组 DNA 序列[NCBI：FJ907395]，与 EU586278 转录本的 5'末端相对应，也在中国普通品种中分离得到，测序表明 FJ907395 包含 EU586278 转录本相应的缺失片段，推断 EU586278 转录本中的缺失片段不存在于基因组中，而可能发生在转录水平。使用 TargetP 软件，预测由 EU586278 编码的假定质体 SSU 的转运肽仅包含 25 个氨基酸，明显短于其他植物 AGP.S.1bs（54-70 个氨基酸）。系统发育树分析表明，EU586278 转运肽的氨基酸序列与其他小麦 Ta.AGP.S1bs[NCBI：AF536819 和 FJ643609]和大麦 AGP.S1b[NCBI：Z48563]的氨基酸序列没有聚类在一起。这表明 EU586278 可能是一种新型的 Ta.AGP.S1b 转录本。半定量 PCR 分析表明，EU586278 的转录本在叶片中大量表达，在内胚乳和茎中中度表达，在根中弱表达。
