Agronomy and Horticulture Department

 

Title

Re-examining the role of ABA as the primary long-distance signal produced by water-stressed roots

Date of this Version

10-2010

Citation

Plant Signaling & Behavior 5:10, 1298-1301; October 2010

Comments

© 2010 Landes Bioscience

(Link goes to publisher's version in PubMed Central)

Abstract

The role of ABA as the primary longdistance signal produced by waterstressed roots and transported to stomata continues to be challenged. We have recently reported that expression of ABA biosynthetic genes in roots only increases in the later stage of water stress. Our results support the hypothesis that in early water stress, increased levels of ABA in xylem sap are due to leaf biosynthesis and translocation to roots and from there to xylem. If so, other xylem-borne chemicals may be the primary stress signal(s) inducing ABA biosynthesis in leaves. We found that apart from ABA, sulfate was the only xylem-borne chemical that consistently showed higher concentrations from early to later water stress. We also found increased expression of a sulfate transporter gene in roots from early water stress onwards. Moreover, using bioassays we found an interactive effect of ABA and sulfate in decreasing maize transpiration rate, as compared to ABA alone. While ABA is undoubtedly the key mediator of water stress responses such as stomatal closure, it may not be the primary signal produced by roots perceiving water stress.