Mutator transposon activation induced by UV-B in Zea mays.

JULIA I. QÜESTA; VIRGINIA WALBOT; PAULA CASATI

Puerto Madryn

Congreso; 46 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2010

Sociedad Argentina de Bioquímica y Biología Vegetal

The Mutator (MuDR/Mu) DNA transposon family in maize includes diverse elements; they all share similar ~215 bp Terminal Inverted Repeats (TIRs), but each has unique internal sequences. MuDR is the regulatory element for the entire system, and the presence of transcriptionally active MuDR elements is required for transposition of the nonautonomous Mu elements. MuDR encodes two genes, mudrA and mudrB. mudrA encodes the transposase, MURA, and mudrB encodes a gene with unknown function. In a previous work, we demonstrated that both mudrA and mudrB transcripts are expressed at higher levels after an 8h-UV-B treatment, in both Mutator active and silencing plants. This transcript increase is accompanied by an increase in histone H3 acetylation and by a decrease in DNA and histone H3 methylation. No changes in the siRNAs were detected. To further evaluate the roll of UV-B in activating Mutator, we performed Chromatin Immuneprecipitation (ChIP) analysis using polyclonal antibodies specific for MURA to assess the in vivo binding capacity of the transposase to its target site in the Mu TIRs. We found that MURA is bound to MuDR TIR in plant leaves treated with UV-B, whereas in control plants no binding was detected. In addition, using plants containing a modified transposon RescueMu, we found that at least in Mutator active plants, novel excision events occur after 8h UV-B treatments.