Plant basal resistance - Universiteit Utrecht

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General discussion
of Arabidopsis mutants in genes that are closely co-regulated with CYP81D11 at the gene
expression level, e.g. At1g05560 (UGT1), At2g29420 (GSTU7), and At4g34138 (UGT73B1),
might be an approach to identify other genes in the pathway.
Figure 2: CYP81D11 as a negative regulator of glucosinolate metabolism and PAMP-induced callose
deposition. A. Over-expression of CYP81D11 in CYP81D11 OE 5-5.3 plants results in increased levels of
4-methoxyindole-3-carboxyaldehde, which is a putative breakdown product of the callose-regulatory
compound 4-methoxyindol-3-ylmethylglucosinolate (4MI3G). Leaf samples were collected from 5
weeks old plants, freeze-dried and analysed by HPLC following extraction. B. Biosynthesis of 4MI3G and
break-down by the atypical myrosinase PEN2 controls PAMP-induced callose in Arabidopsis thaliana.
4MI3G is derived from tryptophan via a multi-step reaction that involves the mono-oxygenases
CYP79B2, CYP79B3, CYP83B1 and CYP81F2. Hydrolisis of 4MI3G by PEN2 leads to the accumuation of
an unknown product that is thought to promote apoplastic callose depostion (Clay et al., 2009). Shown
in red is a putative mechanism by which CYP81D11 suppresses PAMP-induced callose depostion.
EXPLOITATION OF NATURAL VARIATION IN PLANT DEFENCE IN SUSTAINABLE CROP
PROTECTION
How can natural variation be exploited to improve crop protection against diseases and
pests? Although Arabidopsis cannot be considered to be a crop, the availability of genetically
characterised mapping populations and genome-sequenced accessions provides easy
access to the genetic basis of the defence strategies evolved within this species. A potential
disadvantage of this approach is that certain defence traits of Arabidopsis are specific for
Brassicaceae. For instance, glucosinolates play an important role in defence of Arabidopsis
against unadapted insects and pathogens (Tierens et al., 2001; Arany et al., 2008; Bednarek