#+OPTIONS: latex:t
#+LATEX_HEADER: \usepackage{bussproofs}

Maybe by adding  in headers LaTex Header  in the style of a  org file it
could work

\begin{prooftree}
\AxiomC{$A$}
\AxiomC{$A \to \bot$}
\RightLabel{\scriptsize{$\to E$}}
\BinaryInfC{$\bot$}
\end{prooftree}


it works !!!

Thanks a lot Bastien, you are a genius !

Best wishes,

Jo.