Research in the Bogdanove laboratory (updated August 9, 2011 )

Research in the Bogdanove laboratory is grounded in plant bacteriology directed at understanding mechanisms of bacterial plant pathogenesis and plant defense to develop better means of disease control. We primarily study the interactions of rice with pathovars of Xanthomonas oryzae, in which transcription activator-like (TAL) effector proteins of the bacteria play an important role. Despite the "-like," TAL effectors are, in fact, trans-kingdom, positive-acting transcription factors. They are injected into plant cells via the bacterial type III secretion system, imported into the plant cell nucleus, and targeted to effector-specific sites (effector binding elements, or EBEs) in the plant genome. TAL effector binding activates expression of downstream genes, which may contribute to bacterial colonization, symptom development, or pathogen dissemination (reviewed in Bogdanove et al., 2010). We (Moscou and Bogdanove, 2009) and others discovered that TAL effectors recognize their corresponding EBEs in a modular fashion: tandem, polymorphic amino acid repeats in these proteins independently specify single contiguous nucleotides in the DNA target. This correspondence of repeat sequences and target nucleotides makes it possible to derive EBEs for existing TAL effectors and to engineer novel TAL effectors with custom assortments of repeats to bind DNA sequences of choice. Consequently, TAL effectors have received much attention as DNA targeting tools. They have been customized for targeted gene activation, both in plants and in animal cells, and we and others have used them in combination with a fused endonuclease to target DNA double strand breaks for genome engineering (for a review, see Bogdanove and Voytas, 2011, in press). Much of our work therefore centers on better understanding TAL effector DNA targeting, developing improved TAL effector-derived DNA targeting tools, and using those tools in plant genome engineering for disease resistance.

 
   
Bacterial diseases of rice caused by Xanthomonas oryzae pathovars
 
   


Rice is the fifth most valuable crop in the US, a staple worldwide, and an important model for cereal biology for which numerous genetic and genomic resources are in place, including a virtually complete genomic DNA sequence. Bacterial blight and bacterial leaf streak of rice are economically important diseases in many rice-growing regions of the world and are representative of the two major types of disease caused by Gram-negative pathogens in plants. Blight is a vascular disease caused by Xanthomonas oryzae pathovar oryzae. The pathogen enters through wounds or water pores (hydathodes) in the leaf and travels systemically through the plant xylem. Leaf streak is a non-vascular disease caused by Xanthomonas oryzae pv. oryzicola. This pathogen typically enters through stomata and colonizes the intercellular spaces of the leaf photosynthetic tissue. Because the bacteria are members of the same species (they are greater than 90% similar by DNA hybridization studies) and the host is a model cereal, together these diseases constitute a uniquely valuable system for understanding the pathogen and host traits that allow microbes to exploit different plant tissues.

(Under revision, more coming soon. Please see publications for more information)

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    TAL effectors and DNA targeting  
   


(Coming soon. Please see publications for more information.)

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