Functional analysis of genes for tyrosine catabolism that may be involved in annual and perennial differentiation of rice

谷胱甘肽S转移酶(GSTs)是参与细胞内过氧化物质解毒的酶家族，而Zeta类GST(GSTZ)被报道为马来酰乙酰乙酸异构酶(MAAI)，它能解毒酪氨酸和苯丙氨酸分解途径中的同功酸。水稻基因组中含有编码GSTZ基因的两个拷贝。水稻的两个GSTZ基因OsGSTZ1和OsGSTZ2是串联排列的。上游的OsGSTZ1基因结构性表达，而下游的OsGSTZ2基因受胁迫诱导表达。本研究利用RT-PCR技术分析了GSTZ基因在非洲栽培种长粒野生稻和非洲栽培种长粒野生稻中的表达。结果表明，GSTZ1和GSTZ2基因在长秆野生稻中均有表达，而在0。青铜色。因此，通过聚合酶链式反应基因组步行法测定了GSTZ1基因座的基因组序列。序列比较表明，水稻OgGSTZ1基因第8内含子上游的基因组序列与BAC克隆有很高的同源性，与OsGSTZ1基因相差1-Mb以上。这一结果表明OgGSTZ1基因被巨大的重排或倒位所打乱。这一遗传变异与多个品系的非洲野生稻及其祖先野生种巴氏野生稻具有相同之处。OgGSTZ1基因的缺失是一个有趣的现象，OgGSTZ1基因在水稻中的表达水平主要是OsGSTZ2的12倍，并且在水稻和水稻之间存在一些不同的性状，如种子产量和一年生/多年生生境，这些性状可能与氮代谢产物从叶片到种子的转移有关。GSTZ1基因正在被导入到唐山野生稻中，以将一年生生境转变为多年生生境。

Although glutathione S-transferases (GSTs) are family of enzyme involved in the detoxification of per-oxidized materials in cells, Zeta class of GST (GSTZ) is reported as the maleylacetoacetate isomerase (MAAI) which detoxify homogentisate, intermediate in the catabolic pathway of tyrosine and phenylalanine. The genome of rice contains two copies of gene encoding GSTZ. Two GSTZ genes of O. sativa, OsGSTZ1 and OsGSTZ2, lies in tandem-arranged orientation. Upstream OsGSTZ1 gene constitutively expresses whereas downstream OsGSTZ2 gene is inducible by stresses. We analyzed the expression of GSTZ gene in African cultivated species O. glaberrima and wild species O. longistaminata by using RT-PCR. The result showed that both GSTZ1 and GSTZ2 genes expressed in O. longistaminata, whereas only cDNA fragment of downstream GSTZ2 was detected in 0. glaberrima. Thus, the genomic sequence of GSTZ1 locus of O. glaberrima was determined by PCR genomic walking. The sequence comparison between O. sativa and O. glaberrima revealed that genomic sequence upstream from the eighth intron of OgGSTZ1 gene was highly homologous, in inverted orientation, to a BAC clone, apart over 1-Mb from OsGSTZ1 gene in O. sativa. This result suggested that OgGSTZ1 gene was disrupted by huge rearrangement or inversion. The genetic alteration was shared with several lines of O. glaberrima and its ancestral wild species O. barthii. The lost of OgGSTZ1 gene in O. glaberrima is interesting which is mainly expressed 12-fold higher than OsGSTZ2 in O. sativa and some different characters exist between O. sativa and O. glaberrima, like seed yield and annual/perennial habitat that might be related with the translocation of nitrogen metabolites from leaves to seeds. GSTZ1 gene is being introduced into O. glaberrima to convert annual to perennial habitat.