The Cloning And Basic Functional Analysis Of Maize Mediator Subunit MED7 Gene

Corn is one of the most important sources of food for human besides rice and wheat. However, the maize yield is affected seriously by abiotic stress. It is important to explore a series of genes related to abiotic stress response, growth and development processes. Research shows that mediator complex plays important role in flowering regulation of plant development and grain formation. In addition, the mediator complex involved in the stress response by activating the plant’s own defense mechanisms. To clarify the molecular mechanism of mediator complex in the process of corn growth and development, MED7-1 and MED7-2 were cloned from the Q319 cDNA library, which have highly homology with AtMED7. To further analyze the molecular mechanisms and function of ZmMED7-1 and ZmMED7-2, we carried out the expression analysis of MED7-1 and MED7-2 in different tissues of different development stages and tissues treated with ABA as well as other phytohormone. MED7-1 and MED7-2 overexpression in Arabidopsis were developed and stress tolerance assay were performed. Research results in this paper are as follows:(1) MED7-1 and MED7-2 are all expressed in all tested maize tissues and they all have the highest expression in leaves at vegetative growth stage. Their expression level has significant differences in different tissues and developmental stage.(2) The expression of MED7-1 and MED7-2 are up-regulated by BR, IAA, GA3; down-regulated by biological stresses such as ABA, salt and drought.(3) Overexpression of MED7-1 in Arabidopsis significantly reduces the plant tolerance to drought and high salt stress, and they showed lower germination rate compare to wildtype. The effect of overexpression of MED7-2 in Arabidopsis are not so strong as overexpression of MED7-1.(4) MED7-1 and MED7-2 overexpression vector, RNAi vector and FLAG fusion protein expression vector were constructed and transformed into corn, and the MED7-1 overexpression maize were obtained.In summary, MED7 plays an important role in regulating the process of plant stress response. Overexpression of MED7-1 and MED7-2 reduce drought resistance and salt resistance in transgenic Arabidopsis, which provides some basis for maize mediator further study.