Differential expression of molybdenum transport and assimilation genes between two winter wheat cultivars (Triticum aestivum).

Molybdenum (Mo) is an essential trace element for higher plants. Winter wheat cultivar 97003 has a higher Mo efficiency than 97014 under Mo-deficiency stress. Mo efficiency is related to Mo uptake, transfer and assimilation in plants. Several genes are involved in regulating Mo uptake, transfer and assimilation in plants. To obtain a better understanding of the aforementioned difference in Mo uptake, we have conducted a hydroponic trail to investigate the expression of genes related to Mo uptake, transfer and assimilation in the above two cultivars. The results indicate a closed relationship between Mo uptake and TaSultr5.1, TaSultr5.2 and TaCnx1 expression, according to a stepwise regression analysis of the time course of Mo uptake in the two cultivars. Meanwhile, expression of TaSultr5.2 in roots also showed a positive relationship with Mo uptake rates. 97003 had stronger Mo uptake than 97014 at low Mo-application rates (less than 1 μmol Mo L(-1)) due to the higher expression of TaSultr5.2, TaSultr5.1 and TaCnx1 in roots. On the contrary, Mo uptake of 97003 was weaker than 97014 at high Mo application rates (ranging from 5 to 20 μmol Mo L(-1)), which was related to significant down-regulation of TaSultr5.2 and TaCnx1 genes in roots of 97003 compared to 97014. Therefore, we speculated that the differential-expression intensities of TaSultr5.2, TaSultr5.1 and TaCnx1 could be the cause of the difference in Mo uptake between the two winter wheat cultivars at low and high Mo application levels.