Molecular-biological study on the blue light perception system in cyanobacteria

在整个生物界都发现了对蓝光的特定反应。然而，在任何生物体中，蓝光感知及其信号转导的分子机制尚不清楚。聚囊蓝藻PCC6803是一种单细胞蓝藻，可以通过外源添加的DNA自然转化。因此，分子生物学技术可以很容易地应用于菌株。该菌株像其他蓝藻一样在光自养生长（PAG）条件下生长，但也在光异养生长（PHG）条件下生长，以牺牲葡萄糖为代价。该菌株也可以在光激活生长（LAHG）条件下生长，在这种条件下，培养物在黑暗和光照下孵育10分钟，每天一次。在这种条件下，蓝光作为日常脉冲对生长最有效，表明该蓝藻具有蓝光感知及其信号转导系统。在这项研究中，我们分离了4个聚胞菌PCC6803的蓝光不敏感突变体。所有突变体在LAHG条件下均不能生长，而在PAG和PHG条件下均能生长。这些发现表明，这些突变体在参与蓝光感知及其信号转导系统的基因中发生了突变。为了克隆这些基因，用野生型的基因组DNA转化突变体。其中一个突变体（突变体B）被基因组DNA补充。这一发现表明，参与蓝光感知和信号转导系统的基因可以通过突变体的互补从基因组DNA文库中克隆出来。如果基因可以从这个菌株中克隆出来，这将有助于研究生物体是如何感知蓝光并传导信号的。

Blue light specific responses are found throughout the biological kingdoms. However, the molecular mechanism of blue light perception and its signal transduction is not well understood in any organism.The cyanobacterium Synechocystis PCC6803 is a unicellular cyanobacterium which is naturally transformable by exogenously added DNA.Thus, molecular biological techniques can be applied easily to the strain. Thls strain grows under photoautotrophic growth (PAG) condition like other cyanobacteria, but also under photoheterotrophic growth (PHG) condition at the expense of glucose. This strain can also grow under light-activated growth (LAHG) condition in which cultures are incubated in dark and illuminated for 10 min once a day. Blue light is the most effective as daily pulse on the growth under this condition, demonstrating that this cyanobacterium possesses a blue light perception and its signal transduction system.In this study, we have isolated four blue light insensitive mutants of Synechocystis PCC6803. All the mutants are incapable of growing under LAHG condition, but capable of growing under PAG and PHG conditions. These findings suggest that these mutants have mutations in the genes involved in the blue light perception and its signal transduction system. To clone the genes mutants were transformed with the genomic DNA prepared from the wild type. One of the mutants (mutant B) was complemented by the genomic DNA.This finding suggests that the gene involved in the blue light perception and signal transduction system can be cloned from a genomic DNA library by the complementation of the mutant. If the genes could be cloned from this strain, this will lead to study which answers how the organism senses the blue light and transduce the signal.