A smoke-derived butenolide alleviates HgCl2 and ZnCl2 inhibition of water uptake during germination and subsequent growth of tomato--possible involvement of aquaporins.

Aquaporins, concentrated in zones of cell division and enlargement, play a major role in governing the movement of water between neighboring cells during seed germination. The enhanced germination and growth found with smoke-water and butenolide could be the result of better water uptake, suggesting the involvement of aquaporins. The effects of butenolide, known aquaporin inhibitors (HgCl(2) and ZnCl(2)), along with several chemical agents known to reverse the inhibitory effects of mercuric chloride on the activity of aquaporins were tested. Seedlings raised in the presence of butenolide had higher moisture content (93%) compared to those imbibed in water only (85%). This suggests enhanced activity of aquaporins. The presence of aquaporin inhibitors (HgCl(2) and ZnCl(2)) reduced seedling water content and altered root development. The presence of HgCl(2) (10, 20 or 30 microM) reduced the percentage imbibition of seeds by 11-12%. A corresponding gradual decline, from 17.5% (10 microM) to 22.6% (30 microM) (p0.05), in the root length was recorded. Addition of dithiothreitol (DTT, 500 microM), beta-mercaptoethanol (ME, 250 microM) and butenolide (0.1 microM) along with the HgCl(2) overcame the observed inhibitory effects. The presence of ZnCl(2) (12.5 or 25 microM) affected percentage imbibition as well as root length, which was reversed to some extent following addition of the butenolide. Though zinc chloride-mediated inhibition remained unaffected by the presence of DTT and ME, the butenolide reversed the effect. These results are interesting as they suggest additional avenues of research for uncovering the profound effect butenolide has on germination and growth.