Analysis of metal tolerance protein (MTP) family in sunflower (Helianthus annus L.) and role of HaMTP10 as Cadmium antiporter under moringa seed extract

Sunflower (Helianthus annuus L.) is rich source of essential amino acids, omega-6, and linoleic acid, but cadmium (Cd2+) accumulation is hazardous. The higher accumulation of Cd2+ is facilitated by metal tolerance proteins (HaMTPs) in cell membrane of root hairs, and it was hypothyzed that higher expression of a specific antiporter will resist Cd2+ accumulation. We reterived 16 HaMTPs from sunflower genome under Cd2+ stress, and 5% moringa seed extract (MSE). Phylogenetic analysis revealed that HaMTPs were clustered into 7 groups, classified into 5 sub-families, and are true members of cation diffusion facilitators (CDFs) proteins. HaMTP12 have highest 12 introns, HaMTP1 have 11, HaMTP2 have 9, HaMTP9, -10, and -13 have 6, HaMTP11, -12, -14 and -16 have 5, while all 5 members of "E" subfamily have no any intron. RNA-seq and heatmap analysis revealed differential expression of all HaMTPs in selected tissues. Integrative application of 5% MSE increased rate of photosynthesis and similar to 25% yield by upregulating expression of HaMTP10 under Cd2+ stress, confirmed by qRT-PCR. Expression pattern and presence of stress responsive TC-rich, abscisic acid responsive elements (ABRE), and P-box cis-elements indicated stimulation of HaMTPs under MSE and Cd2+ responsiveness. HaMTP10 protein is a member of Mn-CDF subfamily and an antiporter of Cd2+ revealed by gene ontology and transmembrane topology analysis. In conclusion, integrative application of MSE and/or stable overexpression of HaMTP10 provide precise tools to mitigate Cd2+ accumulation in sunflower.