Okada Katsuhiko, Horii Eisuke, Nagashima Yoshiaki, Mitsui Mayuka, Matsuura Hazuki, Fujiwara Shoko, Tsuzuki Mikio
School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan,
Planta. 2015 Jun;241(6):1453-62. doi: 10.1007/s00425-015-2270-z. Epub 2015 Mar 3.
In summary, we could show the involvement of a Hik8-cascade in the expression of genes involved in the glycolytic and OPP pathways induced by GPL, and another signal pathway under photosynthetic conditions in Synechocystis . The Hik8-cascade under GPL conditions may regulate glucose degradation to produce some energy and carbon compounds. This cascade might be important for the supply of organic materials such as amino acids and nucleotides through enhancement of the rates of the glycolysis and OPP pathways. Histidine kinase Hik8 upregulates the expression of one of the important glycolytic genes, fbaA, via sll1330 under heterotrophic growth conditions (i.e., in the presence of glucose with an indispensable short period of light) in Synechocystis sp. PCC 6803. In this study, expression of the genes for the glycolytic and OPP pathways was investigated using the wild type, and disruption mutants of Hik8 and sll1330, to determine whether or not the Hik8-involving signal transduction system generally regulates glucose catabolism. In the wild type, all the genes for the glycolytic and OPP pathways were upregulated under the same conditions as for fbaA. Analyses of the disruption mutants suggested that the signal transduction system involving Hik8 and Sll1330 plays a key role in the upregulation of genes such as pfkA, pgmB, and glk, and also that Hik8 induces genes including gap1 and pgk independently of Sll1330. This complicated signal transduction cascade, designated as the Hik8-cascade, occurs under heterotrophic growth with light pulses. In addition, a disruption mutant of a putative histidine kinase, sll1334, exhibited growth and gene expression patterns that suggested it to be a negative regulator in the cascade. Possible histidine kinases and response regulators as candidates for other components in the cascade are discussed.
总之，我们能够证明Hik8级联参与了由糖脂（GPL）诱导的糖酵解途径和磷酸戊糖途径（OPP）相关基因的表达，以及集胞藻在光合条件下的另一条信号通路。GPL条件下的Hik8级联可能调节葡萄糖降解以产生一些能量和碳化合物。通过提高糖酵解途径和OPP途径的速率，这个级联对于诸如氨基酸和核苷酸等有机物质的供应可能很重要。在集胞藻PCC 6803中，组氨酸激酶Hik8在异养生长条件下（即在有不可缺少的短时光照的葡萄糖存在下）通过sll1330上调重要糖酵解基因之一fbaA的表达。在本研究中，使用野生型以及Hik8和sll1330的缺失突变体研究了糖酵解途径和OPP途径相关基因的表达，以确定涉及Hik8的信号转导系统是否普遍调节葡萄糖分解代谢。在野生型中，与fbaA相同的条件下，糖酵解途径和OPP途径的所有基因均被上调。对缺失突变体的分析表明，涉及Hik8和Sll1330的信号转导系统在pfkA、pgmB和glk等基因的上调中起关键作用，并且Hik8独立于Sll1330诱导包括gap1和pgk在内的基因。这种复杂的信号转导级联，称为Hik8级联，发生在有光脉冲的异养生长条件下。此外，一个假定的组氨酸激酶sll1334的缺失突变体表现出的生长和基因表达模式表明它是该级联中的负调节因子。还讨论了可能作为该级联中其他组分候选者的组氨酸激酶和应答调节因子。
