Migge A, Carrayol E, Hirel B, Lohmann M, Meya G, Becker T W
Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Germany.
Plant Mol Biol. 1998 Jul;37(4):689-700. doi: 10.1023/a:1006005818757.
The photomorphogenetic aurea mutant of tomato severely deficient in spectrophotometrically active phytochromes was used to study the light-regulation of the single-copy nuclear gene encoding plastidic glutamine synthetase (GS-2; EC 6.1.3.2). The de-etiolation of dark-grown aurea mutant seedling cotyledons showed an obligatory dependency on blue light. A limited red light-responsiveness of etiolated aurea cotyledons is, however, retained as seen by the stimulation of both the GS-2 transcript and protein level in the cotyledons of aurea seedlings during growth in red light. The subunits of the octameric GS-2 enzyme were represented by polypeptides with similar electrophoretic mobilities (polypeptides a) in etiolated wild-type or aurea mutant cotyledons. GS-2 proteins with similar apparent molecular masses were also seen in the cotyledons of red light-grown aurea mutant seedlings. In contrast, GS-2 polypeptides with different apparent molecular masses (polypeptides a and b) were detected in the cotyledons of wild-type seedlings grown in red light. This difference indicates that the (post-translational) modification of tomato GS-2 subunit composition is mediated by the photoreceptor phytochrome. The illumination of etiolated wild-type or aurea cotyledons with UV-A- or UV-B-light light resulted in an increase in both the GS-2 transcript and protein level. Following illumination of etiolated wild-type seedlings with UV-A-light, the relative proportion of the GS-2 polypeptides a and b was similar than upon irradiation with blue light but different than after exposure to UV-B- or red light. This result suggests the involvement of a blue/ UV-A-light-specific photoreceptor in the regulation of tomato GS-2 subunit composition.
番茄的光形态建成金黄色突变体严重缺乏分光光度法活性的光敏色素，该突变体被用于研究编码质体谷氨酰胺合成酶（GS-2；EC 6.1.3.2）的单拷贝核基因的光调节。黑暗中生长的金黄色突变体幼苗子叶的去黄化表现出对蓝光的绝对依赖性。然而，黄化的金黄色子叶保留了有限的红光响应性，这可从红光下生长的金黄色幼苗子叶中GS-2转录本和蛋白质水平的刺激中看出。八聚体GS-2酶的亚基由黄化的野生型或金黄色突变体子叶中具有相似电泳迁移率的多肽（多肽a）代表。在红光下生长的金黄色突变体幼苗的子叶中也可见具有相似表观分子量的GS-2蛋白。相比之下，在红光下生长的野生型幼苗子叶中检测到具有不同表观分子量的GS-2多肽（多肽a和b）。这种差异表明番茄GS-2亚基组成的（翻译后）修饰是由光感受器光敏色素介导的。用UV-A或UV-B光照射黄化的野生型或金黄色子叶会导致GS-2转录本和蛋白质水平的增加。用UV-A光照射黄化的野生型幼苗后，GS-2多肽a和b的相对比例与蓝光照射时相似，但与UV-B或红光照射后不同。这一结果表明，一种蓝光/UV-A光特异性光感受器参与了番茄GS-2亚基组成的调节。
