Identification And Analysis Of The MAPK Gene Family In Sorghum Bicolor

Mitogen activated protein kinases (MAPKs) and mitogen activated protein kinases kinases (MAPKKs) form a family of serine/threonine-specific protein kinases that respond to hormonal responses, cell cycle regulation, abiotic stress signaling, and defense mechanisms. However, its tolerant mechanism toward NaCl, Na2CO3, cold and drought has rarely been reported. The availability of sorghum genome made it possible to conduct genome-wide analysis of expression profile of MAPKs and MAPKKs genes in Sorghum bicolor under NaCl, Na2CO3, cold and drought stresses, so as to exploration of the MAPKs and MAPKKs involvement into NaCl, Na2CO3, cold and drought signaling pathway. The results showed that 16 MAPKs and 12 MAPKKs gene were identified from the genome of Sorghum bicolor, namely SbMPKs and SbMKKs, and their expression profiles under NaCl, Na2CO3, drought and cold stresses are significantly different. Under NaCl stress, all SbMPKs were up-regulated continuously in a 24hrs time course except the SbMPK13 whose expression reached to the maximum at around 12hrs. However, only SbMKK1, SbMKK3 and SbMKK8 were up-regulated. Under Na2CO3 stress, SbMPK3, SbMPK10, SbMPK13, SbMKK1, SbMKK3 and SbMKK8 were up-regulated, implying that those six genes are likely responsible specifically for alkaline salt stress in sorghum. Under cold stress, SbMPK10, SbMPK13 and SbMKK8 were up-regulated, implying that those three genes are likely responsible specifically for cold stress in sorghum. Under drought stress, SbMPK13, SbMKK5 and SbMKK8 were up-regulated, implying that those three genes are likely responsible specifically for drought stress in sorghum. Phylogenetic analysis classified SbMPK13 into the C group of MAPKs, a rice homologue OsMAPK2 which was reported to be responsible to ABA and salt stress. This is further confirmed that it involves possibly in the regulation of salt stress response genes in sorghum.