Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 27, 2004
Publication Date: February 7, 2005
Citation: Horvath, D.P., Anderson, J.V., Sonju, R., Jia, Y., Chao, W.S. 2005. The secrets of weed growth and development: new genomic based tools to illuminate the mechanisms. [Abstract]. Weed Science Society of America. Page No. 66.
Interpretive Summary: We have recently cloned a number of genes that are known to play a key role in cell division from the perennial weed leafy spurge. These genes are being used to study the signal transduction processes involved in regulating dormancy and growth in underground buds of this noxious weed. We have shown that several of these genes are up-regulated within 48 hours following growth induction, and are specifically inhibited during induction and maintenance of endo-dormancy (the dormancy that occurs in many perennial plants during the fall). One gene, Cyclin D3, was shown to be directly responsive to growth inducing conditions in other plants, suggesting that it may serve as a powerful tool for identifying factors involved in dormancy release in leafy spurge.
Keywords: growth and development, cell cycle, gene regulation
Understanding mechanisms that control growth and development in weeds will greatly assist in the identification of compounds and practices needed to replace the dwindling repertoire of weed control methods. However, obtaining such information has been hampered by the lack of molecular tools needed to study these processes. To address this shortcoming, we have collected DNA sequence data on key regulatory genes involved in meristem growth and development from EST databases of various species. These sequences were aligned and regions that were highly conserved between various species were identified. Specific primers were then designed to amplify these genes from leafy spurge. To date, we have cloned sequences from key cell cycle regulatory genes including A and D class Cyclins, and Cyclin Dependent Kinase (CDK) inhibitors such as KRP4, and should soon have clones of B class cyclins as well. We have also identified clones for the Retinoblastoma protein (Rb), CDK Activating Kinase (CAK), Histone Deacetylase (HDAC), and numerous other cell cycle and developmental regulatory genes from the EST databases of several cDNA libraries produced from leafy spurge. Expression of these genes has been followed in underground adventitious shoot buds of leafy spurge (often referred to as root and crown buds in the literature) following treatments known to effect dormancy. Plants were harvested monthly throughout the year, and after loss of apical dominance. Plants were also treated with the growth regulating hormone gibberellic acid (GA). KRP4, HDAC, CAK, and Rb show minor changes in expression levels under conditions that alter growth or dormancy status in root or crown buds of leafy spurge. The CycD and CycA genes are all up-regulated within 48 hrs following loss of para-dormancy or GA treatment. CycD is known to be regulated at the transcriptional level by growth inducing signals in Arabidopsis. This up-regulation can occur in the presence of the translational inhibitor cycloheximide, indicating that CycD is directly responsive to growth regulating signals. Promoter sequences for CycD from leafy spurge have been obtained and comparisons to the orthologous Arabidopsis genes have allowed the identification of several conserved motifs which likely interact directly with components of the growth regulating processes.