Zhu Y S, Hearst J E
Proc Natl Acad Sci U S A. 1986 Oct;83(20):7613-7. doi: 10.1073/pnas.83.20.7613.
RNA levels were measured by blot hybridization to study the coordinate and differential expression of Rhodobacter capsulatus genes for light-harvesting I antenna proteins LH-I and LH-II; reaction center (RC) polypeptides L, M, and H; and bacteriochlorophyll and carotenoid biosynthesis in response to light and O2. The genes for LH-II alpha and beta subunits only have one transcript, 0.5 kilobase (kb) long, whereas the genes for LH-I have two transcripts (0.5 and 2.6 kb). The small transcript (0.5 kb) is the mRNA only for LH-I beta and alpha polypeptides, whereas the large transcript (2.6 kb) codes for RC-L, RC-M, and the beta and alpha polypeptides of LH-I, as well as the product of an unknown open reading frame designated ORF C2397. These five genes thus comprise a single operon (designated the puf operon). The mRNA specifying the LH-II polypeptides is more abundant, more sensitive to changes in O2 concentration, and shows a variation over a wider range than that of the mRNA for LH-I, indicating that the genes for LH-II and LH-I/RC are regulated independently. The gene for RC-H (puhA) has at least two transcripts (1.2 and 1.4 kb) that initiate within ORF F1696 and respond differentially to light intensity. The expression of the genes coding for RC-L, RC-M, and RC-H is coordinately regulated by light intensity and O2 concentration. An increase in light intensity causes a decrease in the expression of the genes for LH-I, LH-II, and RC proteins. The genes coding for the enzymes in the bacteriochlorophyll biosynthetic pathways are regulated by light intensity and O2 in a manner similar to that of the genes for LH and RC proteins. The crt genes coding for the enzymes in carotenoid biosynthetic pathways, however, are regulated in an opposite fashion: high light intensity results in increased expression of crt genes. These results are interpreted based on the protective function of carotenoids under high light intensity in the presence of O2.
通过印迹杂交测量RNA水平，以研究荚膜红细菌中光捕获I天线蛋白LH-I和LH-II、反应中心（RC）多肽L、M和H以及细菌叶绿素和类胡萝卜素生物合成相关基因在响应光和氧气时的协同表达与差异表达。LH-II α和β亚基的基因只有一个0.5千碱基（kb）长的转录本，而LH-I的基因有两个转录本（0.5 kb和2.6 kb）。小转录本（0.5 kb）仅是LH-I β和α多肽的mRNA，而大转录本（2.6 kb）编码RC-L、RC-M以及LH-I的β和α多肽，还有一个未知开放阅读框（命名为ORF C2397）的产物。这五个基因因此组成一个单一操纵子（命名为puf操纵子）。指定LH-II多肽的mRNA更丰富，对氧气浓度变化更敏感，并且比LH-I的mRNA显示出更宽范围的变化，表明LH-II和LH-I/RC的基因是独立调控的。RC-H（puhA）的基因至少有两个转录本（1.2 kb和1.4 kb），它们在ORF F1696内起始并对光强度有不同反应。编码RC-L、RC-M和RC-H的基因的表达受光强度和氧气浓度的协同调控。光强度增加会导致LH-I、LH-II和RC蛋白基因的表达下降。细菌叶绿素生物合成途径中编码酶的基因受光强度和氧气调控的方式与LH和RC蛋白基因类似。然而，类胡萝卜素生物合成途径中编码酶的crt基因则以相反的方式调控：高光强度导致crt基因表达增加。基于类胡萝卜素在高光强度和有氧气存在时的保护功能对这些结果进行了解释。
