Location: Crops Pathology and Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
Evaluate the aquaporin-regulated hydraulic response of various grapevine rootstocks to salinity and test the ability of calcium to ameliorate this stress. Evaluate the aquaporin-regulated hydraulic response of various grapevine rootstocks to a range of abiotic factors (i.e., drought, anoxia, nutrient-pulses, chilling) and their influence on known grapevine rootstock vigor classifications. Utilize the molecular evidence from the physiological analysis to develop rapid markers suitable for salinity tolerance selection. Manipulate aquaporin activity of grapevine roots via irrigation/fertigation management to improve grapevine vigor and fruit quality.
1b. Approach (from AD-416)
A variety of grapevine rootstocks and species will be grown both hydroponically and in potting soil in greenhouses. We will measure the hydraulic conductivity of excised fine roots and whole root systems using ultra-low flowmeters and cell pressure probe technologies and whole root systems using pressure chambers. Functional aquaporin activity will be assessed by measuring reductions in hydraulic conductivity of individual fine roots and whole root systems after treatment with known aquaporin inhibitors. Molecular aquaporin activity will initially be evaluated using aquaporin molecular probes previously developed for grapevines. Over the long term, aquaporin protein abundance and immunolocalization analysis in fine roots will be conducted. Documents Reimbursable Agreement with American Vineyard Foundation. Log 41322.
3. Progress Report
This agreement was established in support of objective 3 of the in-house project, the goal being to develop sustainable water management practices for vineyards. The goal of this project is to evaluate the aquaporin-regulated hydraulic response of various grapevine rootstocks to stress. Gene expression of aquaporins (water-specific protein channels found in plant cell membranes) was found to be significantly in high vigor and drought resistant grapevine rootstocks compared to those with low vigor and drought intolerance, but this did not directly correlate with altered hydraulic conductivity for fine roots. To better understand why the differences in aquaporin gene expression among rootstocks did not correlate with fine root hydraulic conductivity, we utilized Laser Capture Micro-dissection (LCM) to determine the exact location of aquaporin expression in different root tissues (i.e. epidermis, cortex, endodermis, vasculature) and along the length of the root. We found that expression is much greater at the root tip and limited to the vascular tissue in older portions of the root system (i.e. lignified portions 20-30 cm back from the root tip). Expression of aquaporins inside the vasculature (i.e. at the center of the root) would not alter the radial permeability of the whole root tissue. We also found that water uptake can occur the entire length of the root and not just where aquaporins are predominantly expressed. This demonstrates that we must consider the root system as a whole, and that aquaporins likely play an important role in sensing stress as the root tip explores the soil but not in altering the permeability of these woody root systems as a whole. This work resulted in manuscript submission to the Journal of Experimental Botany.