Many potted plants like Kalanchoe¨ have an
elongated natural growth habit, which has to be controlled
through the application of growth regulators. These
chemicals will be banned in the near future in all the EU
countries. Besides their structural functions, the importance
of homeotic genes to modify plant architecture appears
evident. In this work, the full length cDNA of five KNOX
(KN) genes were sequenced from K. x houghtonii, a
viviparous hybrid. Two constructs with the coding
sequence of the class I and class II homeobox KN genes,
KxhKN5 and KxhKN4, respectively, were overexpressed in
the commercially important ornamental Kalanchoe¨ blossfeldiana
‘Molly’. Furthermore, a post-transcriptional gene
silencing construct was made with a partial sequence of
KxhKN5 and also transformed into ‘Molly’. Several
transgenic plants exhibited compact phenotypes and some
lines had a relative higher number of inflorescences.
A positive correlation between gene expression levels and
the degree of compactness was found. However, a correlation
between the induced phenotypes and the number
of inserted copies of the transgene were not observed,