The research concerned the selection of new Arabidopsis mutants disturbed
in the growth of the roots in general, and in particular in gravitropism
and circumnutational movements. In the year 2002 the cloning of the AtRHA1
gene, that characterizes the Atrha1 mutant of Arabidopsis, was pursued.
This mutant, isolated from the Feldmann collection of T-tagged mutants
some years ago, shows in the roots reduced gravitropic response and
notable resistance to the plant hormones auxin and ethylene. In the year
2002 the cDNA of the gene was isolated and transferred in the mutant
obtaining the complementation. This confirmed that the mutation was
effectively due to the presence of the T-DNA in the gene AtRHA1. The gene
is new and belongs to the Heat Shock Factors, e.g. to a family of
transcription factors which, apart their function in the activation of
the Heat Shock Proteins, show also functions in different processes. We
think the gene is involved in the transduction of signals coming from
auxin and gravity. In addition, the genetic and physiogical
characterization of the mutant P58 has been pursued. This mutant is
totally agravitropic in the roots. Furthermore, the data regarding the
growth of Arabidopsis roots, both from wild-type ecotypes, and from the
mutants eir1, aux1, rha1, 1-6C, on the Random Positioning Machine have
been elaborated. This apparatus, which basically is a two axes clinostat,
is able to produce with notable precision conditions of simulated absence
of gravity, close to those present in space on the ISS or on flying
satellites. The results show as Arabidopsis roots from the wild-types
grow on this machine following large loops to the right-hand, and thus by
making a movements of circumnutationto the right-hand. By contrast, In
the gravitropic and auxinic mutants the growth of the roots is
essentially random. Auxin therefore appears to be involved not only in
gravitropism, but also in chiral circumnutation.
Focus