Increased expression of a plant actin gene during a biotrophic interactionbetween round-leaved mallow, Malva pusilla, and Colletotrichum gloeosporioides f. sp malvae
Sm. Jin et al., Increased expression of a plant actin gene during a biotrophic interactionbetween round-leaved mallow, Malva pusilla, and Colletotrichum gloeosporioides f. sp malvae, PLANTA, 209(4), 1999, pp. 487-494
Two actin genes, actA from the hemibiotrophic anthracnose fungus, Colletotr
ichum gloeosporioides (Penz.) Pent. & Sacc. f. sp. malvae, and act1 from it
s host, Malva pusilla (Sm.) were cloned from a cDNA library developed from
infected host tissue. The actin gene, actA, of C. gloeosporioides f. sp. ma
lvae, which is similar to that of other euascomycetes, appears to be expres
sed constitutively. The actin gene of M. pusilla is most similar to one of
the actin genes of Arabidopsis thaliana that is unique in being responsive
to environmental stimuli such as wounding. Expression of actA was used to f
ollow the growth of the fungus in the plant tissue. Low actA expression occ
urred until 72-96 h after inoculation and then increased rapidly, correspon
ding with the timing of the shift from slower biotrophic fungal growth to m
uch more rapid necrotrophic growth. In contrast, expression of act1 approxi
mately doubled during the biotrophic phase and then rapidly declined during
the necrotrophic phase. Increased host actin expression could be due to ho
st cytoskeleton rearrangement in response to biotrophic infection, and the
subsequent decrease in host actin expression could be due to host cell disr
uption resulting from tissue maceration during necrosis. This is the first
report of a host actin gene that can increase in expression during a compat
ible plant-pathogen interaction.