Rapid shoot-to-root signalling regulates root hydraulic conductance via aquaporins.
We investigated how root hydraulic conductance (normalized to root dry weight, Lo ) is regulated by the shoot. Shoot topping (about 30% reduction in leaf area) reduced Lo of grapevine (Vitis vinifera L.), soybean (Glycine max L.) and maize (Zea mays L.) by 50 to 60%. More detailed investigations with soybean and grapevine showed that the reduction in Lo was not correlated with the reduction in leaf area, and shading or cutting single leaves had a similar effect. Percentage reduction in Lo was largest when initial Lo was high in soybean. Inhibition of Lo by weak acid (low pH) was smaller after shoot damage or leaf shading. The half time of reduction in Lo was approximately 5 min after total shoot decapitation. These characteristics indicate involvement of aquaporins. We excluded phloem-borne signals and auxin-mediated signals. Xylem-mediated hydraulic signals are possible since turgor rapidly decreased within root cortex cells after shoot topping. There was a significant reduction in the expression of several aquaporins in the plasma membrane intrinsic protein (PIP) family of both grapevine and soybean. In soybean, there was a five- to 10-fold reduction in GmPIP1;6 expression over 0.5-1 h which was sustained over the period of reduced Lo .
Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus PMB 1, Glen Osmond, South Australia, 5064, Australia.
Rebecca K
RK
Vandeleur
Wendy
W
Sullivan
Asmini
A
Athman
Charlotte
C
Jordans
Matthew
M
Gilliham
Brent N
BN
Kaiser
Stephen D
SD
Tyerman
D020346:Aquaporins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism; D018526:Plant Transpiration; D015398:Signal Transduction; D013025:Glycine max / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D027843:Vitis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014867:Water / Q000378:metabolism*; D052584:Xylem; D003313:Zea mays / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D020346:Aquaporins; D010940:Plant Proteins; D014867:Water
grapevine; maize; plasma membrane intrinsic protein; root hydraulic conductivity; soybean