Abstract
BackgroundMaize (Zea mays L.) is a widely cultivated cereal and has been used as an optimum heavy metal phytoremediation crop. Metallothionein (MT) proteins are small, cysteine-rich, proteins that play important roles in plant growth and development, and the regulation of stress response to heavy metals. However, the MT genes for maize have not been fully analyzed so far.MethodsThe putative ZmMT genes were identified by HMMER.The heat map of ZmMT genes spatial expression analysis was generated by using R with the log2 (FPKM + 1).The expression profiles of ZmMT genes under three kinds of heavy metal stresses were quantified by using qRT-PCR. The metallothionein proteins was aligned using MAFFT and phylogenetic analysis were constructed by ClustalX 2.1. The protein theoretical molecular weight and pI, subcellular localization, TFs binding sites, were predicted using ProtParam, PSORT, PlantTFDB, respectively.ResultsA total of 9 ZmMT genes were identified in the whole genome of maize. The results showed that eight of the nine ZmMT proteins contained one highly conserved metallothio_2 domain, while ZmMT4 contained a Metallothio_PEC domain. All the ZmMT proteins could be classified into three major groups and located on five chromosomes. The ZmMT promoters contain a large number of hormone regulatory elements and hormone-related transcription factor binding sites. The ZmMT genes exhibited spatiotemporal specific expression patterns in 23 tissues of maize development stages and showed the different expression patterns in response to Cu, Cd, and Pb heavy metal stresses.ConclusionsWe identified the 9 ZmMT genes, and explored their conserved motif, tissue expression patterns, evolutionary relationship. The expression profiles of ZmMT genes under three kinds of heavy metal stresses (Cu, Cd, Pb) were analyzed. In summary, the expression of ZmMTs have poteintial to be regulated by hormones. The specific expression of ZmMTs in different tissues of maize and the response to different heavy metal stresses are revealed that the role of MT in plant growth and development, and stress resistance to heavy metals.
Highlights
Maize (Zea mays L.) is a widely cultivated cereal and has been used as an optimum heavy metal phytoremediation crop
These results suggest that ERF and MYB may play an important role in regulating ZmMT gene expression
Using the PlantRegMap to analyze the binding elements on the promoter, the results showed that the promoters of ZmMT2, ZmMT7, and ZmMT9 have a large number of ERF binding components, the promoters of ZmMT2 and ZmMT6 have a large number of MYB or MYB-related transcription factor (TF) binding components, while the promoter of ZmMT9 has a large number of NAC TF binding components, the promoter of ZmMT7 has a large number of LBD binding components, the promoters of ZmMT3, ZmMT5 and ZmMT9 has a large number of WRKY binding elements
Summary
Maize (Zea mays L.) is a widely cultivated cereal and has been used as an optimum heavy metal phytoremediation crop. Metallothionein (MT) proteins are small, cysteine-rich, proteins that play important roles in plant growth and development, and the regulation of stress response to heavy metals. The 6 MT genes in sugarcane (Saccharum officinarum L.) were found, which ScMT3-1 plays an active role in yeast (P. pastoris) response to Cd2+ and Cu2+ stress[35].Previous investigations showed that plant MT proteins acted as reactive oxygen species (ROS) scavenging enzymes [19, 36,37,38]. The expression level of MT1 in the root cortex was found to decrease during aerenchyma formation under waterlogged conditions [41] These findings suggested that MT proteins had a role in determining the fate of cells in roots during inducible aerenchyma formation
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