AsgD, a new two-component regulator required for A-signalling and nutrient sensing during early development of Myxococcus xanthus
AsgD, a new two-component regulator required for A-signalling and nutrient sensing during early development of Myxococcus xanthus
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DOI：
10.1046/j.1365-2958.1999.01594.x
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发表时间：
1999-10-01
影响因子：
3.6
通讯作者：
Zusman, DR
中科院分区：
文献类型：
--
作者：
Cho, KY;Zusman, DR
黄色粘球菌有一个复杂的生活史，包括子实体的形成。发展的最初阶段之一被称为A-信令。ASG(A信号)突变体被认为在产生A信号方面存在缺陷，导致早期发育受阻。本文报道了一个新的ASG基因座asgD的鉴定。该基因座似乎同时参与了环境感知和细胞间信号传递。在营养生长过程中未检测到asgD的表达，饥饿1h后，asgD的表达显著增加。AsgD蛋白被预测含有773个氨基酸，是一个双组分调控系统的一部分，因为它在N端有一个接收域，在C端有一个组氨酸蛋白激酶。1个asgD缺失突变体在CF子实体形成和产孢量方面存在缺陷。然而，当细胞与野生型菌株或与bsgA、csgA、dsgA或esgA突变体混合时，突变体的缺陷可以在细胞外得到补充，但不能被asgA、asgB或asgC突变体在细胞外补充。此外，突变体还被A因子氨基酸的一个子集拯救。令人惊讶的是，当突变体被培养在严格的饥饿培养液中而不是CF上时，细胞能够形成子实体。因此，AsgD似乎直接或间接参与了对营养限制条件的感知。AsgD基因座的发现为黄曲霉的早期发育提供了重要的感觉转导成分。
Myxococcus xanthus has a complex life cycle that includes fruiting body formation. One of the first stages in development has been called A-signalling. The asg (A-signalling) mutants have been proposed to be deficient in producing A-signal, resulting in development arresting at an early stage. In this paper, we report the identification of a new asg locus asgD. This locus appears to be involved in both environmental sensing and intercellular signalling. Expression of asgD was undetected during vegetative growth, but increased dramatically within 1 h of starvation. The AsgD protein is predicted to contain 773 amino acids and to be part of a two-component regulatory system because it has a receiver domain located at the N-terminus and a histidine protein kinase at the C-terminus. An asgD null mutant was defective in fruiting body formation and sporulation on CF medium. However, the defects of the mutant were complemented extracellularly when cells were mixed with wild-type strains or with bsgA, csgA, dsgA or esgA mutants, but were not complemented extracellularly by asgA, asgB or asgC mutants. In addition, the mutant was rescued by a subset of A-factor amino acids. Surprisingly, when the mutant was plated on stringent starvation medium rather than CF, cells were able to form fruiting bodies. Thus, it appears that AsgD is directly or indirectly involved in sensing nutritionally limiting conditions. The discovery of the asgD locus provides an important sensory transduction component of early development in M. xanthus.