Gene Expression Pattern of Vacuolar-Iron Transporter-Like (VTL) Genes in Hexaploid Wheat during Metal Stress

Abstract

Iron is one of the important micronutrients that is required for crop productivity and yield-related traits. To address the Fe homeostasis in crop plants, multiple transporters belonging to the category of major facilitator superfamily are being explored. In this direction, earlier vacuolar iron transporters (VITs) have been reported and characterized functionally to address biofortification in cereal crops. In the present study, the identification and characterization of new members of vacuolar iron transporter-like proteins (VTL) was performed in wheat. Phylogenetic distribution demonstrated distinct clustering of the identified VTL genes from the previously known VIT genes. Our analysis identifies multiple VTL genes from hexaploid wheat with the highest number genes localized on chromosome 2. Quantitative expression analysis suggests that most of the VTL genes are induced mostly during the Fe surplus condition, thereby reinforcing their role in metal homeostasis. Interestingly, most of the wheat VTL genes were also significantly up-regulated in a tissue-specific manner under Zn, Mn and Cu deficiency. Although, no significant changes in expression of wheat VTL genes were observed in roots under heavy metals, but TaVTL2, TaVTL3 and TaVTL5 were upregulated in the presence of cobalt stress. Overall, this work deals with the detailed characterization of wheat VTL genes that could provide an important genetic framework for addressing metal homeostasis in bread wheat.

Vacuolar Iron Transporter (Like) proteins: Regulators of cellular iron accumulation in plants

“…These results seem to suggest specific a role for the each of the groups. Analysis in tomato, soybean, and wheat revealed that around 60–70% of the VIT/VTL genes are located on only one or two chromosomes and vast majority of them are present in tandem (Cao, 2019; Sharma et al, 2020). These results suggest that tandem duplication, segmental duplication, and transposition have been major factors in expansion of the VIT/VTL genes in different plant species.…”

“…A recent study has shown that mutation in OsVITs results in decreased Fe in leaf sheath, nodes and aleurone but increased Fe in blade and grains (Che et al, 2021). The rice genome also contain five VTL genes (Sharma et al, 2020). In recent RNA‐Seq study, it was observed that OsVTL2 has strong expression in endosperm compared to the embryo and pericarp (Ram et al, 2020).…”

“…These data indicate that TaVIT1 is able to transport iron but it may localize to the plasma membrane (Connorton, Jones, et al, 2017). Recently gene expression response of different TaVTL genes was also analyzed under altered mineral and heavy metal stress conditions (Sharma et al, 2020). Table 1 highlights altered gene expression of TaVTL genes under different conditions.…”

Structure and function of the vacuolar Ccc1/VIT1 family of iron transporters and its regulation in fungi

“…The presence of more than one homolog in several archaea and bacteria species and the high domain diversity in prokaryotes (next section) support a complex evolutionary history for this protein family. In plants, several transpositions and both segmental and tandem duplication events contributed to generate an elevated number of Ccc1/VIT1 proteins with specialized functions ( Supplementary Table S1 ) [36] , [37] . In a lesser extent, gene expansions have also occurred in some clades of fungi like the genus Aspergillus and Penicillium , Glomeromycota division, and Mucoromycotina and Agaricomycotina subdivisions .…”

Annotation and Molecular Characterisation of the TaIRO3 and TaHRZ Iron Homeostasis Genes in Bread Wheat (Triticum aestivum L.)

“…Recent progress in bread wheat genetics, such as the release of a fully annotated genome sequence and newly integrated databases, has allowed for efficient in silico gene identification [ 24 , 25 , 26 , 27 , 28 ]. The availability of these genetic resources has recently led to a boom in molecular characterisation efforts of wheat genes involved in Fe transport, chelation, and storage; however, there has been little characterisation of upstream regulators of Fe homeostasis to date [ 29 , 30 , 31 , 32 , 33 ]. Genes from diploid (2n) species, such as rice, often have three orthologous sequences (referred to as homoeologs) in the hexaploid (AABBDD = 6n) bread wheat genome.…”