ICOM1 Abstract
session: Monday (Physiology) or Tuesday (gene
expression)
BALAJI. BOOVARAGHAN, ARMAND SEGUIN & YVES PICH. CRBF, Universit Laval,
Ste-Foy, Qubec G1K 7P4, Canada.-Expression of PAL and CHS mRNAs during
appressoria formation in a non-mycorrhizal (Myc-) and colonization in a
mycorrhizal (Myc+) transformed roots of pea (Pisum sativum L.)
Arbuscular mycorrhizal (AM) fungi associate with most of the vascular
plants for which they provide nutrients and protect against drought and
plant pathogens. Though the physiology of the AM symbioses has been
extensively studied, little is known of the biochemical and genetic
processes involved. Following microbial attack, plants accumulate
phytoalexins, phenylalanine ammonia-lyase (PAL) activity and the
corresponding PAL or chalcone synthase (CHS) mRNAs. PAL and CHS are
regulatory enzymes of flavonoid and isoflavonoid biosynthesis. In our
present study, we examined the accumulation of phytoalexins and the
expression of PAL and CHS mRNA in the transformed roots of pea (Pisum
sativum L.) cv.Frisson following inoculation with a AM fungus, Glomus
intraradices (Schenck & Smith) during different stages of AM
colonization, viz; contact, penetration and colonization of AM fungi.
We have established transformed roots cultures of pea, either resistant
to AM invasion (Myc-), or normally AM colonized parental line, Frisson
(Myc+). Pisatin, a phytoalexin of pea, was analyzed by HPLC and
Northern blot hybridization was done to study the expression of PAL and
CHS mRNAs. Our model with Ri T-DNA transformed roots of Myc- and Myc+
pea would allow one to eliminate other contaminating microbes and
provides an ideal system for physiological and genetic studies.