טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBassani Sternberg Michal
SubjectMolecular Growth Regulation in Plant Roots under Water
Stress: Identification of Genes Associated with
Root Growth and Drought Resistance
DepartmentDepartment of Biology
Supervisor Professor Emeritus Shimon Gepstein


Abstract

Growth in the apical elongation zone of plant roots is central to the development of functional root systems. Rates of root segmental elongation change from accelerating to decelerating as cell development proceeds. One of the primary variables regulating these changes in elongation rates is the extensibility of the elongating cell walls. To help decipher the complex molecular mechanisms involved in spatially-variable root growth, we performed a gene identification study along primary root tips of maize seedlings using suppression subtractive hybridization (SSH). Using SSH, we isolated 150 non redundant cDNA clones representing root growth-related genes that were preferentially expressed in the elongation zone. Differential expression patterns were found for 50 genes isolated by SSH and several candidate genes. Genes were classified into groups based on the predicted function: cell wall metabolism, cytoskeleton, general metabolism, signaling and unknown. In-situ hybridization performed for two selected genes, confirmed the spatial distribution shown by Northern blots and revealed subtle differences in tissue localization. Spatial profiles of expression for some cell wall related genes appeared to correlate with the profile of accelerating root elongation and changed appropriately under growth-inhibitory water deficit. A functional confirmation of the unknown gene RG240B as a subunit of the vacuolar ATPase complex is shown by yeast complementation technique. To determine the regulatory role for a putative transcription factor; zinc finger gene, transformation of Arabidopsis was performed. This study provides new important information regarding new biochemical processes, pathways and cellular events associated with the regulation of root elongation.