Jang J C, León P, Zhou L, Sheen J
Department of Genetics, Harvard Medical School, Massachusetts General Hospital, Boston 02114, USA.
Plant Cell. 1997 Jan;9(1):5-19. doi: 10.1105/tpc.9.1.5.
The mechanisms by which higher plants recognize and respond to sugars are largely unknown. Here, we present evidence that the first enzyme in the hexose assimilation pathway, hexokinase (HXK), acts as a sensor for plant sugar responses. Transgenic Arabidopsis plants expressing antisense hexokinase (AtHXK) genes are sugar hyposensitive, whereas plants overexpressing AtHXK are sugar hypersensitive. The transgenic plants exhibited a wide spectrum of altered sugar responses in seedling development and in gene activation and repression. Furthermore, overexpressing the yeast sugar sensor YHXK2 caused a dominant negative effect by elevating HXK catalytic activity but reducing sugar sensitivity in transgenic plants. The result suggests that HXK is a dual-function enzyme with a distinct regulatory function not interchangeable between plants and yeast.
高等植物识别并响应糖类的机制在很大程度上尚不清楚。在此，我们提供证据表明，己糖同化途径中的首个酶——己糖激酶（HXK），作为植物糖类响应的传感器发挥作用。表达反义己糖激酶（AtHXK）基因的转基因拟南芥植株对糖类反应不敏感，而过量表达AtHXK的植株则对糖类反应过度敏感。这些转基因植株在幼苗发育以及基因激活和抑制方面表现出广泛的糖类反应改变。此外，过量表达酵母糖类传感器YHXK2会通过提高HXK催化活性但降低转基因植株的糖类敏感性而产生显性负效应。结果表明，HXK是一种具有独特调节功能的双功能酶，其在植物和酵母之间不可互换。
