Abstract
P1B-type ATPases, known as heavy metal ATPases (HMAs), play an important role in the control of cadmium (Cd) accumulation in plants. In this study, a total of 12 ZmHMA genes were identified in the maize genome and particularly classified into six clusters based on their phylogenetic relationship and motif compositions. Furthermore, the expression patterns of different ZmHMA genes varied with developmental stages, and were tissue specific under normal conditions. ZmHMA2 and ZmHMA3 genes exhibited significant up-regulation under Cd treatment. Eventually, the association analysis between 103 inbred lines and alleles in ZmHMA2 and ZmHMA3 revealed that one insertion–deletion (InDel) in the intron from ZmHMA2 was associated with leaf Cd concentration under low Cd condition at the seedling stage. Twenty polymorphisms in ZmHMA3 were significantly associated with leaf Cd concentration under various Cd levels at seedling and maturing stages. Five single nucleotide polymorphisms (SNPs) and two InDels of these significantly associated polymorphic loci from ZmHMA3 caused the amino acid substitutions and insertion or deletion events. Importantly, the proteins encoded by ZmHMA2 and ZmHMA3 genes were located in the plasma membrane. This comprehensive analysis will provide an important theoretical basis for future functional verification of ZmHMA genes to unravel the mechanisms of Cd accumulation in leaves of maize. Additionally, the favorable alleles in ZmHMA3 will lay a foundation for the marker-assisted selection of low Cd accumulation in maize.
Highlights
Heavy metal contamination in soil has become a severe problem in many parts of the world, which threatens human life through the food chain (Li et al, 2014a)
P1B-type ATPases (HMAs) in maize were identified using the cloned OsHMA2 (Oryza sativa Japonica) and OsHMA3 (Oryza sativa Japonica) as protein queries in BLASTP searches against the B73 reference genome sequence
A variant in C-terminal region perform regulatory roles in OsHMA3 activity (Kumagai et al, 2014). All these results indicated that the variants on the C-terminal region of ZmHMA3 played an important role in controlling Cd accumulation of maize during the entire growth period
Summary
Heavy metal contamination in soil has become a severe problem in many parts of the world, which threatens human life through the food chain (Li et al, 2014a). Cadmium (Cd) is one of the most toxic heavy metals present in the soil environment and is readily. Genome-wide identification of ZmHMAs and association of natural variation in ZmHMA2 and ZmHMA3 with leaf cadmium accumulation in maize. Most of the Cd accumulation in the aboveground tissues, especially in the leaves of maize has become a main source of Cd intake in numerous developing countries as maize has been used as agricultural raw materials and as a feedstock for livestock for many years. A better understanding of the mechanism of Cd accumulation in maize is an important step for breeding programs in developing varieties with low Cd accumulation
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