Plant basal resistance - Universiteit Utrecht

Chapter 5
Figure 1: CYP81D11 regulates flg22-induced callose depostion. Leaves from hydroponically cultivated
8-day- old seedlings of the wild-type (Col-0), a CYP81D11 T-DNA knock-out line (CYP81D11 KO), and an
over-expression line (CYP81D11 OE 5-5.3) were treated with either flg22 (0.1 mM) or mock solution.
At 24 h after treatment, cotelydons were collected for aniline blue staining, UV-epifluoresence
microscopy, and digital quantification of callose intensity as described (Luna et al., 2011). Shown
are relatively callose intensities (% callose-corresponding area). Photographs show representative
differences in fluorescent callose signals under UV-epifluoresence microscopy.
Since the PEN2-dependent break-down product(s) of 4-methoxyindol-3-
ylmethylglucosinolate (4MI3G) has been found to act as major regulator of PAMP-induced
callose (Clay et al., 2009), and CYP81 enzymes have been shown to modulate the biosynthesis
of indolic glucosinolates (Pfalz et al., 2011), it is tempting to hypothesize that CYP81D11
regulates callose by scavenging the callose-inducing break-down product of 4MI3G. To test
this hypostasis, we analysed the CYP81D11OE line for endogenous IG levels and break-
down products thereof. Although there were no statistically significant differences in total
amounts of IGs, these preliminary results revealed increased accumulation of several IG
breakdown products, of which 4-methoxyindole-3-carboxaldehyde was the most noticeable
(Figure 2A). These findings point to the possibility that CYP81D11 inhibits callose formation
through conversion of the callose-inducing PEN2 product into 4-methoxyindole-3-
carboxaldehyde (Figure 2B). More experiments need to be carried out to get a more definite
outcome concerning this matter. Furthermore, studying PAMP-induced callose phenotypes
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