Gene expression patterns in wheat coleorhiza under cold- and biological stratification.

This study assessed germination of wheat seeds under cold and biological stratification and determined the expression level of gibberellins (GA) and abscisic acid (ABA) genes in coleorhiza. Both cold and biological stratification significantly (P<0.05) enhanced the rate and efficacy of germination. The spatial distance between the fungal endophyte and the seed can be a determining factor of biological stratification as seeds in direct contact with fungal endophyte showed the highest rate and efficacy of germination. Consistently high expression of GA3ox2 gene was found in wheat coleorhiza throughout the tested period of germination. The expression of ABA biosynthesis gene, TaNCED, was substantially higher in cold stratification seeds, reflecting the role of abscisic acid in stress-adaptation. Overall, this study provides molecular evidence of the importance of coleorhiza in germinating wheat seeds, in addition to reporting that the spatial distance between symbiotic partners may be a critical factor driving mycovitality.