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Activation of a maize alpha-tubulin promoter and tubulin
location in mycorrhizal transgenic tobacco roots
poster/talk
5.Gene Expression
BONFANTE, PAOLA1, A. GENRE1, R.
BERGERO1, P. PUIGDOMENECH2
1Dipartimento di Biologia vegetale
dell'Università, CSMT-CNR, Viale Mattioli 25, 10125
Torino, Italy
2Departament de Genetica Molecular. CID-CSIC.
Jordi Girona, 18. 08034 Barcelona, Spain
ICOM1 Abstract
Transformed tobacco plants are good hosts for AM fungi and
were used to test the hypothesis that changes in the
expression of cytoskeleton genes are involved in the
substantial morphological modifications described in root
cells upon fungal colonization. Tobacco plants containing
constructs where the promoters of either a maize a1 or an a3
tubulin gene were fused with the GUS reporter gene showed an
intense GUS activity in the meristematic region. When
colonized by Gigaspora margarita, only plants with the tuba3
construct showed gene activation in the differentiated root
regions. We have detected i) GUS activity in the cortical
root cells which contain arbuscules, and ii) accumulation of
a3 tubulin transcripts in maize root cells where arbuscules
are formed.
Immunofluorescence experiments revealed an altered pattern of
expression of alpha and beta tubulins in the infected
cells. Microtubules organization in the apical root meristeme
reveals the different mitotic phases, while microtubular
bundles in the parenchymatic cortical cells showed reduction
both in thickness and in number. The penetration of the
symbiotic fungus into these cortical cells caused a change in
organization of microtubules. They run along the
intracellular hyphae and the arbuscular trunk, and branch
around the small arbuscular hyphae as short bundles. In
conclusion, on the basis of GUS technology and in situ
hybridization, we offer evidence that tuba3 gene changes its
expression during establishment of symbiosis with AM fungi in
both maize and transgenic tobacco. In addition,
immunofluorescence clearly reveals that microtubules
represent another cellular compartment that changes its
organization upon fungal colonization.