Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2009
Publication Date: 11/5/2009
Citation: Thilmony, R.L., Guttman, M.E., Thomson, J.G., Blechl, A.E. 2009. The LP2 leucine-rich repeat receptor kinase promoter directs organ-specific, light-responsive expression in transgenic rice. Plant Biotechnology Journal. 7:867-882.
Interpretive Summary: Crop biotechnology has the potential to improve the productivity of U.S. agriculture. Tools to precisely control gene expression in grass species like rice and wheat are needed. Promoters are the genetic switches which determine when and where genes are expressed. The rice LP2 promoter has been isolated and shown to activate gene expression only in leaves and other green tissues of transformed rice plants. This promoter is off or only very weakly expressed in the roots, mature seeds and other non-green tissues. The LP2 promoter is stimulated by light exposure and thus rice seedlings grown in the dark have low or undetectable levels of expression. The spatial distribution of gene expression mediated by the LP2 promoter is the highest in leaf mesophyll cells, but expression is also detected in other leaf cell types as well. Organ-specific promoters like LP2 will enable precise, localized expression of transgenes in biotechnology-derived crops and limit the potential of unintended impacts on plant physiology and the environment.
Technical Abstract: Biotechnologists seeking to limit gene expression to non-seed tissues of genetically engineered cereal crops have only a few choices of well characterized organ-specific promoters. We have isolated and characterized the promoter of the rice Leaf Panicle 2 gene (LP2, Os02g40240). The LP2 gene encodes a leucine-rich repeat-receptor kinase-like protein that is strongly expressed in leaves and other photosynthetic tissues. Transgenic rice plants containing an LP2 promoter-GUS::GFP bifunctional reporter gene displayed an organ-specific pattern of expression. This expression corresponded to transcript levels observed on RNA blots of various rice organs and microarray gene expression data. The strongest ß-glucuronidase (GUS) activity was observed in histochemically stained mesophyll cells, but other green tissues and leaf cell types including epidermal cells also exhibited expression. Low or undetectable levels of LP2 transcript and LP2-mediated reporter gene expression were observed in roots, mature seeds, and reproductive tissues. The LP2 promoter is highly responsive to light and only weak expression was detected in etiolated rice seedlings. The specificity and strength of the LP2 promoter suggests that this promoter will be a useful control element for green tissue-specific expression in rice and potentially other plants.