PT  - JOURNAL ARTICLE
AU  - Anita Kurilla
AU  - Timea Toth
AU  - Laszlo Dorgai
AU  - Zsuzsanna Darula
AU  - Tamas Lakatos
AU  - Daniel Silhavy
AU  - Zoltan Kerenyi
AU  - Geza Dallmann
TI  - Nectar- and stigma-specific expression of a chitinase could partially protect against fire blight in certain apples
AID  - 10.1101/606046
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 606046
4099  - http://biorxiv.org/content/early/2019/04/11/606046.short
4100  - http://biorxiv.org/content/early/2019/04/11/606046.full
AB  - To attract pollinators many angiosperms secrete stigma exudate and nectar in their flowers. As these nutritious fluids are ideal infection points for pathogens, both secretions contain various antimicrobial compounds. Erwinia amylovora, the causing bacterium of the devastating fire blight apple disease, is the model pathogen that multiplies in flower secretions and infects through the nectaries. Although Erwinia resistant apples are not available, certain cultivars are tolerant. It was reported that in stigma infection assay, the ‘Freedom’ cultivar was Erwinia tolerant while the ‘Jonagold’ was susceptible. We hypothesized that differences in the nectar protein compositions lead to different susceptibility. Indeed we found that an acidic chitinase III protein (Machi3-1) selectively accumulates in the nectar and stigma of the ‘Freedom’ cultivar. We demonstrate that MYB binding site containing repeats of the ‘Freedom’ Machi3-1 promoter are responsible for the strong nectar- and stigma-specific expression. As we found that in vitro the Machi3-1 protein impairs growth and biofilm formation of Erwinia at physiological concentration, we propose that the Machi3-1 contribute to the tolerance by inhibiting Erwinia multiplication in the stigma exudate and in the nectar. We show that the Machi3-1 allele was introgressed from Malus floribunda 821 into different apple cultivars including the ‘Freedom’.Highlight Certain apple cultivars accumulate to high levels in their nectar and stigma an acidic chitinase III protein that can protect against pathogens including fire blight disease causing Erwinia amylovoraMachi3-1Malus acidic chitinase 3-1 protein