Transcriptome and biochemical analysis pinpoint multi-layered molecular processes associated with iron deficiency tolerance in hexaploid wheat

Iron (Fe) is an essential nutrient for plants that is indispensable for many physiological activities. Although few genotypes were identified with contrasting tolerance to Fe deficiency, the molecular insight into the distinct biochemical and transcriptional responses determining the trait is poorly known. This study aimed to identify the molecular and biochemical basis for the contrasting Fe deficiency tolerance in wheat genotype showing tolerance to Fe deficiency (cv. Kanchan-KAN) compared to susceptible (cv. PBW343-PBW) cultivar. Under Fe deficiency, the KAN show delayed chlorosis, high SPAD values and low malondialdehyde activity compared to PBW. The shoot transcriptomics studies show that a large set of genes for photosynthetic pathways were highly induced in PBW, suggesting its sensitivity to Fe deficiency. Although, under Fe deficiency, both the cultivars show distinct molecular re-arrangements, including high expression of genes involved in Fe uptake (including membrane transporters) and mobilization, the gene expression level was higher in KAN. Furthermore, the KAN cultivar also shows high ubiquitination activity in the shoot tissue suggesting a high turnover of proteins in the tolerant cultivar. These observations were also co-related with the high root phytosiderophores biosynthesis and its release that contributes to the enhanced Fe translocation index in KAN. Overall, our work provides the key link to understanding the mechanistic insight for the Fe deficiency tolerance in hexaploid wheat. This will enable wheat breeders to select genotypes for better Fe use efficiency for agriculture.