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Mario SOBERON - Mardi 5 décembre 2017 14h

Auditorium - Bât. 442 - Séminaire Micalis

 Mario SOBERON - Mardi 5 décembre 2017 14h
Dual mode of action of Bacillus thuringiensis Cry toxins

Dual mode of action of Bacillus thuringiensis Cry toxins

Mario SOBERON

Universidad Nacional Autónoma de México

Transgenic crops that produce Bacillus thuringiensis (Bt) proteins for pest control are grown extensively, but insect adaptation can reduce their effectiveness.  The established mode of action models assert that Bt three domain proteins Cry1Ab and Cry1Ac are produced as inactive protoxins of 130 kDa that require conversion to 60 kDa activated form to exert toxicity. The 60 kDa three domain activated toxins undergo a sequential binding to different insect gut proteins, as cadherin, aminopetidase N or alkaline phosphatase, facilitating the formation of a pre-pore oligomer structure that inserts into the cell membrane forming pores that lead to midgut cell burst and death of larvae. However, it was recently shown that Cry1Ab protoxin binds cadherin receptor leading to a pre-pore oligomer structure that differs from the pre-pore oligomer formed from activated toxin. Both pre-pores contribute to toxicity indicating that protoxins are also active and a dual mode of action of three domain Cry toxins was proposed. Furthermore, analysis of toxicity of Cry1Ab and Cry1Ac to different lepidopteran populations resistant to Cry1A toxins showed that most populations are resistant to activated Cry1A toxins but are sensitive to protoxins, supporting the dual mode of action of Cry toxins. We will revise the data supporting the dual mode of action of Cry1Ab toxin and protoxins. We will also report further characterization on the mode of action of Cry protoxins. The data indicates that having two distinct modes of action of Cry insecticidal proteins could provide means for improving toxicity and delaying resistance to these important proteins.

Mardi 5 décembre 2017

14h

Auditorium - Bât. 442

INRA, Jouy en Josas

Invité par Didier Lereclus