氨基酸对大麦根中硝酸盐吸收和还原系统的差异效应。

Differential effect of amino acids on nitrate uptake and reduction systems in barley roots.

作者信息

Aslam M, Travis R L., Rains D W.

机构信息

Department of Agronomy and Range Science, University of California, One Shields Avenue, 95616-8515, Davis, CA, USA

出版信息

Plant Sci. 2001 Jan 5;160(2):219-228. doi: 10.1016/s0168-9452(00)00391-5.

DOI:10.1016/s0168-9452(00)00391-5

PMID:11164593

Abstract

This study was conducted to determine whether the inhibition of nitrate reductase activity (NRA; EC 1.6.6.1) in barley (Hordeum vulgare L. var. CM-72) roots by the amino acids (glutamic, aspartic, glutamine and asparagine) is a direct effect or indirect due to inhibition of the NO(3)(-) uptake system. Roots of 8-day-old intact seedlings were supplied with the amino acids (I mM) individually either with NO(3)(-) (0.1 or 10 mM) or roots were pretreated with the amino acids and then supplied with NO(3)(-) only. Nitrate uptake was determined by following NO(3)(-) depletion from the uptake solution containing 0.1 mM NO(3)(-). All the amino acids inhibited the increase in NO(3)(-) uptake similarly (50-60%) when the roots were supplied with 0.1 mM NO(3)(-). Pretreatment with glutamic and aspartic acids was more inhibitory (70-80%) than with glutamine and asparagine (30%). The amino acids partially inhibited (35%) the induction of NRA in roots supplied with 0.1 mM NO(3)(-); however, no inhibition occurred at 10 mM NO(3)(-). Likewise, pretreatment with glutamic or aspartic acid inhibited the induction of NRA at 0.1 mM NO(3)(-) but not at 10 mM NO(3)(-). In contrast, pretreatment with glutamine or asparagine had no effect on the subsequent induction of NRA, even at 0.1 mM NO(3)(-). The results suggest that, at low NO(3)(-) supply, the inhibition of induction of NRA by the amino acids is a result of the lack of substrate availability due to inhibition of the NO(3)(-) uptake system.

摘要

本研究旨在确定氨基酸（谷氨酸、天冬氨酸、谷氨酰胺和天冬酰胺）对大麦（Hordeum vulgare L. var. CM - 72）根系硝酸还原酶活性（NRA；EC 1.6.6.1）的抑制作用是直接效应还是由于对NO₃⁻吸收系统的抑制而产生的间接效应。向8日龄完整幼苗的根系分别单独供应氨基酸（1 mM），同时供应NO₃⁻（0.1或10 mM），或者先用氨基酸预处理根系，然后仅供应NO₃⁻。通过跟踪含有0.1 mM NO₃⁻的吸收溶液中NO₃⁻的消耗来测定硝酸盐吸收。当根系供应0.1 mM NO₃⁻时，所有氨基酸对NO₃⁻吸收增加的抑制作用相似（50 - 60%）。用谷氨酸和天冬氨酸预处理的抑制作用更强（70 - 80%），而谷氨酰胺和天冬酰胺的抑制作用为30%。氨基酸对供应0.1 mM NO₃⁻的根系中NRA的诱导有部分抑制作用（35%）；然而，在10 mM NO₃⁻时未发生抑制。同样，用谷氨酸或天冬氨酸预处理在0.1 mM NO₃⁻时抑制NRA的诱导，但在10 mM NO₃⁻时无此现象。相反，用谷氨酰胺或天冬酰胺预处理对随后NRA的诱导没有影响，即使在0.1 mM NO₃⁻时也是如此。结果表明，在低NO₃⁻供应条件下，氨基酸对NRA诱导的抑制是由于NO₃⁻吸收系统受到抑制导致底物可利用性缺乏的结果。