Verbruggen N, Borstlap A C, Jacobs M, Van Montagu M, Messens E
Department of Genetics, Flanders Interuniversity Institute for Biotechnology, Universiteit Gent, Belgium.
Planta. 1996;200(2):247-53. doi: 10.1007/BF00208315.
The raz1 mutant of Arabidopsis thaliana (L.) Heynh. has been selected as resistant to the toxic proline analogue, azetidine-2-carboxylic acid (2AZ). Seedlings of the mutant tolerated fivefold higher concentrations of 2AZ (ED50 = 0.25 mM) than the wild-type seedlings (EC50 = 0.05 mM). The mutant gene was found to be semi-dominant and the corresponding RAZ1 locus was mapped on chromosome 5 at 69.6 +/- 1.8 cM. The resistance to 2AZ could be fully and exclusively accounted for by the lower uptake rate of the proline analogue in the mutant. The influx of L-proline in roots of wild-type seedlings could be dissected into two components: (i) a component with a high affinity and a low capacity for L-proline (Km) approximately 20 microM, Vmax approximately 60 nmol.(g FW)-1.h-1) and also a high affinity for L-2AZ (Ki approximately 40 microM) and (ii) a low-affinity, high-capacity component (Km) approximately 5 mM: Vmax = 1300 nmol.(g FW)-1.h-1). Clearly, the raz1 mutation affects the activity of a high-affinity transporter, because the high-affinity uptake of proline in the mutant was at least fivefold lower than in the wild-type, whereas the low-affinity uptake was unchanged.
拟南芥（Arabidopsis thaliana (L.) Heynh.）的raz1突变体已被选作对有毒脯氨酸类似物氮杂环丁烷-2-羧酸（2AZ）具有抗性的品种。该突变体幼苗耐受2AZ的浓度比野生型幼苗高五倍（ED50 = 0.25 mM），而野生型幼苗的EC50 = 0.05 mM。发现该突变基因是半显性的，相应的RAZ1基因座被定位在第5号染色体上，距离为69.6±1.8 cM。对2AZ的抗性可以完全且唯一地由突变体中脯氨酸类似物较低的摄取率来解释。野生型幼苗根中L-脯氨酸的流入可分为两个部分：（i）一个对L-脯氨酸具有高亲和力和低容量的部分（Km约为20 microM，Vmax约为60 nmol·(g FW)-1·h-1），并且对L-2AZ也具有高亲和力（Ki约为40 microM）；（ii）一个低亲和力、高容量的部分（Km约为5 mM；Vmax = 1300 nmol·(g FW)-1·h-1）。显然，raz1突变影响了一种高亲和力转运蛋白的活性，因为突变体中脯氨酸的高亲和力摄取比野生型至少低五倍，而低亲和力摄取则没有变化。
