This has led to a concentration of study on PIP rather that TIP and meant that virtually nothing was known about how TIPs acted in processes such as seed maturation and germination. The University of Warwick's research team work not only resulted in the most complete plant TIP expression map produced to date - it also threw up a major surprise in that they found that TIP not only had a role to play in water management in seed maturation and germination - in fact they found that it probably plays the crucial water management role, as PIP was almost literally nowhere to be seen.
As PIP, but not TIP, are generally found at the plasma membrane of plant cells, one would expect the involvement of PIP in seed de/rehydration. Intriguingly, however, the Warwick researchers studied microarray datasets and found that - out of 13 PIPs encoded by the Arabidopsis genome - only 3 (PIP1;2, PIP1;4, PIP1;5) seemed to be detectable in their seeds. They also found that those 3 PIPs did not show up until 60 hours after germination, i.e. only after the end of the most important phases of water uptake in a germinating seed. In contrast the researchers found that very high levels of TIP3 protein appeared to be present in the plasma membrane during seed development and germination.
Dr Frigerio's working hypothesis is that TIP3, besides residing in the tonoplast, is recruited to the plasma membrane to compensate for the absence (or very low concentration) of PIP. We are now on the right path to build a real understanding of how water uptake is regulated in seed development and germination. That understanding will help researchers produce seeds to meet the challenges of Global climate change, and food security through improved drought resistance and increased water use efficiency.
|Contact: Peter Dunn|
University of Warwick