Potential Role of TIP3 Aquaporins in the Transport of HO and Boric Acid During Seed Development and Germination in Soybean (Glycine max L.).

Tonoplast intrinsic proteins (TIPs) are the channel-forming proteins predominantly found in the tonoplast of plant cells. Despite the identification of TIPs in numerous plant species, very less is known about the precise role of different TIP subgroups. In the present study, two genes belonging to the TIP3 subgroup were studied to understand tissue-specific role and solute transport activity. The soybean GmTIP3-1 and GmTIP3-2 were found to be expressed exclusively in seeds. Unlike rest of the aquaporins (AQPs), the expression of GmTIP3s gradually increased during seed maturation. The GmTIP3s also show higher expression during the initiation of seed germination, suggesting their potential role in the solute transport during seed maturation and germination. Further, GmTIP3-1 and GmTIP3-2 were functionally characterised to understand the structure, pore morphology, pore hydrophobicity, sub-cellular localization, and solute specificity. The solute specificity of TIPs is crucial in various physiological and developmental processes. Solute transport activity studied using yeast growth and survivability assay suggests that GmTIP3-1 and GmTIP3-2 can transport hydrogen peroxide (HO) and boric acid, both of which are known to play significant role in seed germination. The information provided here will help to understand the precise role of TIP3 genes in seed development and germination.