Expression of genes encoding PIP aquaporins in tomato seeds exposed to blue radiation and mercury

Abstract

Aquaporins control the specific transport of water and some other small molecules across membranes and are involved in various physiological processes. Plasma membrane aquaporins (PIPs) were shown to play an important role during tomato seed development. Therefore, we were interested in the participation of PIPs in seed germination and early seedling growth of wild type (WT) and the 7B-1 mutant, affected by blue light responses. We characterised the expression patterns of PIP-type aquaporin genes in these lines during different phases of seed germination and seedling growth after HgCl2 (an aquaporin blocker) treatment. Further, we investigated whether blue radiation (BL) was involved in the regulation of these processes. Our experiments showed that 7B-1 mutant seed germination and root elongation are less responsive to HgCl2 compared to WT. In both WT and 7B-1 mutant seeds, BL modulates the expression of PIP1;1 (upregulation) and PIP1;3 (downregulation) aquaporin isoforms. The PIP1;3 gene is downregulated not only by BL but also by HgCl2 with a stronger effect in WT seeds. Thus, we show that BL can alter PIPs gene expression during tomato seed germination and seedling growth and that the 7B-1 mutation reduced the responsiveness to mercury blockage of aquaporins. Altogether, our data indicate that PIP aquaporins participate in tomato seed germination and radicle elongation and that the 7B-1 mutation and BL have an impact on these processes.