Metal Tolerance Proteins (MTPs) are the class of membrane proteins involved in the transport of metals, mainly Zn, Mn, Fe, Cd, Co and Ni, and confer metal tolerance in plants. In the present study, a comprehensive molecular analysis of rice MTP genes was performed to understand the evolution, distribution and expression dynamics of MTP genes. Exploration of the whole genome re-sequencing information available for three thousand rice genotypes highlighted the evolution and allelic diversity of MTP genes. Based on the presence of non-synonymous single nucleotide polymorphism (SNP), MTP1, MTP6, MTP8 and MTP9 were found to be the most conserved genes. Furthermore, results showed localization of MTP1, MTP8.1 and MTP9, and MTP11, respectively with QTLs/m-QTLs for Zn and Cd accumulation, making these genes promising candidates to understand the QTL regulation. Expression profiling of the entire set of 10 MTP genes revealed root and shoot specific expressions of MTP9 and MTP8.1, respectively, under all tested vegetative stages. Expression of seed-specific MTPs increased as seed maturation progressed, which revealed their potential role in transporting metals during seed filling. Upon exposure to harmful heavy metals, expression of most MTP genes decreased in root and increased in shoot, suggests that different mechanisms are being employed by MTPs in different tissues. Contrastingly, only a few MTPs were found to be responsive to Fe and/or Zn starvation conditions. The extensive analysis of MTPs presented here will be helpful in identifying candidate MTP genes for crop biofortification and bioremediation purposes.

Insertional mutagenesis is an indispensable tool for engendering a mutant population using exogenous DNA as the mutagen. The advancement in the next-generation sequencing platform has allowed for faster screening and analysis of generated mutated populations. Rice is a major staple crop for more than half of the world’s population; however, the functions of most of the genes in its genome are yet to be analyzed. Various mutant populations represent extremely valuable resources in order to achieve this goal. Here, we have reviewed different insertional mutagenesis approaches that have been used in rice, and have discussed their principles, strengths, and limitations. Comparisons between transfer DNA (T-DNA), transposons, and entrapment tagging approaches have highlighted their utilization in functional genomics studies in rice. We have also summarised different forward and reverse genetics approaches used for screening of insertional mutant populations. Furthermore, we have compiled information from several efforts made using insertional mutagenesis approaches in rice. The information presented here would serve as a database for rice insertional mutagenesis populations. We have also included various examples which illustrate how these populations have been useful for rice functional genomics studies. The information provided here will be very helpful for future functional genomics studies in rice aimed at its genetic improvement.