Cloning and Expression Analysis of Triose Phosphate/Phosphate Translocator Gene from Wheat

Triose phosphate translocator (TPT) is located in the inner membrane of plant chloroplasts. It catalyzes the counter exchange of those phosphate/3-phosphoglycerate and phosphate. To obtain the basic information on the structure-function relation, a cDNA encoding the complete precursor of the triose phosphate translocator has been isolated from wheat (Triticum aestivum L.) by RACE ( rapid amplification of cDNA ends) strategies. The wheat TPT cDNA encodes a precursor protein of 402 amino acid residues with a deduced molecular weight of 43 kD. A putative processing site between Ala-78 and Ala-79 of the precursor protein is suggested by comparison with those of the TPTs from spinach (Spinacia oleracea Mill.) and maize (Zea mays L.). The mature part of wheat TPT consists of 324 amino acid with a molecular weight of 35 kD, which share 89% identity with maize TPT. The amino acids Lys-274 and Arg-275 (mature protein) which is regarded as the substrate-binding site, are both conserved in plant TPTs. The gene expression analysis for leaves, coleoptiles, roots and seeds of wheat showed that the TPT transcript was only detectable in leaves and coleoptiles. No apparent expression signal was detected in the roots and seeds. This indicated that the expression of wheat TPT might be restricted to green tissues.

DNA sequence analysis of the triose phosphate isomerase gene from isolates of Giardia lamblia

Objective To confirm the genetic relation between Giardia lamblia (G. lamblia) isolates from different geographic regions of China and other countries.Methods Genomic DNA were extracted from the trophozoites or cysts of Giardia lamblia. The triose phosphate isomerase (tim) gene was amplified using polymerase chain reaction (PCR) technique. PCR products were digested with endonuclease and sequenced. The data of sequencing were analyzed with the DNAstar software and compared with that of the isolates acquired from GenBank.Results Of nine isolates of Giardia lamblia from China (C1, C2, CH2 and CH3), Cambodia (CAM), Australia (A1 and A2) and America (BP and CDC), respectively, 3 (A1, A2 and CAM) fit into Group 1 (WB), 2 (CH2 and CH3)) into Group 2, and 4 (C1, C2, BP and CDC) into Group 3 (GS). The results confirmed the genetic relatedness of G. lamblia isolates from all over the world.Conclusion Genotyping isolates of G. Lamblia provides important information for establishing the phylogenetic relationship or for the epidemiological evaluation of the spreading of this organism.

茶树3个TPT基因的鉴定与表达

【目的】进行茶树磷酸丙糖转运蛋白(Triose phosphate translocator,TPT)基因鉴定和表达模式分析,为探索其基因功能和茶树抗性育种提供理论参考。【方法】基于茶树全基因组序列,利用生物信息学方法筛选鉴定TPT基因,分析其在茶树不同组织中的表达特性及其在冷胁迫、干旱胁迫、盐胁迫、茉莉酸甲酯(MeJA)处理和硒处理中的表达情况。【结果】从茶树基因组中鉴定到3个含有TPT结构域的基因,序列长度为807~1635 bp,分别编码268~544个氨基酸;3个TPT蛋白均呈弱碱性或者碱性,均为稳定蛋白、疏水蛋白;亚细胞定位预测3个TPT蛋白位于质膜或叶绿体;系统进化分析将茶树TPT分为2组,基因结构和保守基序分析表明,3个茶树TPT基因结构和保守结构域大致相同;启动子顺式作用元件分析表明,茶树TPT基因的启动子区含有多个光反应、胁迫和激素等响应元件。基因表达分析发现CsTPT3在芽和叶片中有较高的表达,可能与茶树光合作用有关;CsTPT2在不同逆境下均呈现出显著下调表达的趋势,推测该基因在应对茶树低温、干旱、MeJA、盐和外源高浓度硒等胁迫过程中起着负调控作用。【结论】CsTPT基因可能参与了茶树响应逆境胁迫的过程。

N/P/K Ratios and CO₂Concentration Change Nitrogen-Photosynthesis Relationships in Black Spruce

The relationship between photosynthesis and leaf nitrogen concentration is often used to model forest carbon fixation and ratios of different nutrient elements can modify this relationship. However, the effects of nutrient ratios on this important relationship are generally not well understood. To investigate whether N/P/K ratios and CO2 concentration ([CO2]) influence relationships between photosynthesis and nitrogen, we exposed one-year-old black spruce seedlings to two [CO2] (370 and 720 μmol·mol-1), two N/P/K ratio regimes (constant (CNR) and variable (VNR) nutrient ratio) at 6 N supply levels (10 to 360 μmol·mol-1). It was found that photosynthesis (Pn) was more sensitive to nitrogen supply and N/P/K ratios under the elevated [CO2] than under ambient [CO2];under the elevated [CO2], Pn declined with increases in N supplies above 150 μmol·mol-1 in the CNR treatment but was relatively insensitive to N supplies of the same range in the VNR treatment. Further, our data suggest that the nutrient ratio and the CO2 elevation effects on photosynthesis were via their effects on the maximum rate of carboxylation (Vcmax) but not electron transport (Jmax) or triose phosphate utilization (TPU). The results suggest that the CO2 elevation increased the demand for all three nutrient elements but the increase was greater for N than for P and K. The CO2 elevation resulted in greater photosynthetic use efficiencies of N, P and K, but the increases varied with the nutrient ratio treatments. The results suggest that under elevated [CO2], higher net photosynthetic rates demand different optimal N-P-K ratios than under the current [CO2].