Different Expression of Segmentally Duplicated ZmMPK6-1 and ZmMPK6-2 Paralogues in Maize

Aims: ZmMPK6-1 and ZmMPK6-2 are two genes resulting from segmental duplication in the maize genome. To investigate whether ZmMPK6-1 and ZmMPK6-2 had different expression or functions, we designed and conducted this experiment.
Methodology: Adult plants and 10-day-old seedlings of maize were used to study the expression of ZmMPK6-1 and ZmMPK6-2 in different tissues. The responses of ZmMPK6-1 and ZmMPK6-2 to polyethylene glycol (PEG6000, 25%, w/v), NaCl (200 mM), abscisic acid (ABA, 100 ìM), salicylic acid (SA, 1 mM), or hydrogen peroxide (H2O2, 2 mM) were performed in 10-day-old seedlings.
Results: Although ZmMPK6-1 and ZmMPK6-2 are highly similar to each other throughout the entire coding sequence (95.32% identity), gene-specific primers can be generated based on the portions of 5’-untranslated region (UTR) of the two genes which share only 37.97% identity. The organ-specific expression of ZmMPK6-1 and ZmMPK6-2 in adult plants and 10-day-old showed that, although the two genes share high sequence identity, they have differently expressional patterns in different tissues. They have also dissimilarly expressional patterns in response to PEG6000 (25%, w/v), NaCl (200 mM), ABA (100 ìM), SA (1 mM), or H2O2 (2 mM).
Conclusion: ZmMPK6-1 and ZmMPK6-2 paralogoues displayed markedly different patterns of expression in different tissues or in response to different stimuli, suggesting that differently functional roles may have been distributed to the two genes after evolutionary duplication.