Kinetic properties of NADP(+)-malic enzyme in two populations of the C-4 weed species Echinochloa crus-galli (L.) Beauv. (Poaceae) from sites of contrasting climates

被引:9
作者
Dubuc, M. [1 ]
Lapointe, L. [1 ]
Simon, J. -P. [1 ]
机构
[1] Univ Montreal, Dept Sci Biol, Montreal, PQ H3C 3J7, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
Thermal acclimation; C-4; metabolism; NADP(+)-malic enzyme; catalytic properties; apparent energy of activation; K-m; V-max; ecotypes. barnyard grass;
D O I
10.2307/2389408
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
Plants from two populations of the C-4 grass Echinochloa crus-galli (L.) Beauv. from Quebec (QUE) and Mississippi (MIss), were acclimated under controlled conditions at 28/22 degrees C, 21/15 degrees C and 14/8 degrees C (day/night). The apparent energy of activation (E-a), Michaelis-Menten constant (K-m for malate), V-max, V-max/K-m ratios and specific activity of NADP(+)-malic enzyme (E.C. 1.1.1.40) were investigated. Electrophoresis disclosed one molecular form for the enzyme with a molecular weight of 280,000 daltons and similar electrophoretic mobility for the two populations. E-a values obtained for NADP(+)-ME from QUE plants acclimated to 14/8 degrees C were significantly lower than those of MISS plants in the 15-30 degrees C assay temperatures but, no such differences were found under higher acclimatory conditions. K-m values decreased as a function of assay temperature and, except for 40 degrees C assays, there were no significant differences between populations or between thermoperiods for this parameter. V-max values and V-max/K-m ratios were higher for the enzyme of plants of both populations grown at 14/8 degrees C and significantly higher in QUE plants as compared to MISS plants acclimated to 14/8 degrees C. NADP(+)-ME activities were significantly higher in QUE plants as compared to MISS plants acclimated to 28/22 degrees C or 21/15 degrees C but not at 14/8 degrees C. For both populations, enzyme activities were significantly reduced at 14/8 degrees C as compared to those measured at higher thermoperiods. The modifications in kinetic properties of NADP(+)-ME among the two Echinochloa populations do not explain the chilling sensitivity of this chloroplastic enzyme in MISS plants and suggest that the cause might be associated to chloroplast disfunction.
引用
收藏
页码:353 / 362
页数:10
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