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SESSION 1: FUSARIUM – GENETICS, GENOMICS AND SYSTEMS BIOLOGY
P4 - Studying gene expression in fungus and planta to
understand the interaction Fusarium verticillioidesmaize
I. Lazzaro 1 , P. Battilani 1 , A. Lanubile 2 , A. Marocco 2
1 Institute of Entomology and Plant Pathology; 2 Institute of Agronomy, Genetics and Field Crops,
University Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy
E-mail: alessandra.lanubile@unicatt.it
Fusarium verticillioides is a plant pathogen able to produce fumonisin in maize
kernels. A study on the pathosystem F. verticillioides-maize has been developed
speculating on both in vitro and in planta perspectives. The former studied the
effects of temperature (T) and water activity (aw) on fumonisin B (FB) production
and expression of FUM genes in F. verticillioides strains. The latter monitored
which genes were differentially expressed in resistant and susceptible maize lines
at several time points after inoculation by a fumonisin-producing strain of F.
verticillioides.
The in vitro study showed that FUM gene expression was sensibly affected by aw,
rather than T, indicating that fungal metabolism is more overturned by low aw than
by T decrease. Most of FUM genes were highly expressed at aw=0.990 compared
to 0.955, similarly to FB production, underlining that gene expression and
secondary metabolite production followed the same trend. At 21 days of
incubation, FUM14 and FUM3 -regulating the production of FB1 and FB2 from FB3
and FB4, respectively – were maximally expressed, while FUM21 – coding for a
transcription factor for FB biosynthesis – was 10x less expressed; aw=0.900 was
inhibitory for culture growth and FB production.
The in planta study showed that in kernels at 48 h after inoculation (hai) about
800 genes were differentially regulated and nearly 10% assigned to the defence
category. During the very early stages of incubation a small proportion of the host
transcripts was induced and none of them was involved in defence processes.
Early response genes encoded signalling or regulatory components. The highest
number of differentially expressed genes was attained at 48 hai. The late
response genes encoded effector proteins. When resistant and susceptible maize
genotypes were compared, in the resistant line the expression of defence genes
was detected before inoculation, while in the susceptible genotype they were
induced only after pathogen inoculation.
Keywords: Fusarium, maize, fumonisin, biosynthesis, defence genes
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