A strawberry mitogen-activated protein kinase gene, FaMAPK19, is involved in disease resistance against Botrytis cinerea

Abstract

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules involved in a wide range of resistance strategies against pathogen attack. However, the function of strawberry (Fragaria × ananassa) MAPKs in resistance against Botrytis cinerea remains unclear. The present study investigated the functional role of FaMAPK19 in the regulation of defense responses in strawberry fruit to B. cinerea. Changes in FaMAPK19 expression levels throughout whole-plant development and phenotypes of strawberry fruit after B. cinerea inoculation exhibited strong relationships with the level of FaMAPK19 transcripts and severity of gray mold. Transient transformation was carried out to overexpress FaMAPK19 and its antisense transcript in strawberry fruits, which were later analyzed upon B. cinerea inoculation. The distinct phenotypes of transformed fruits indicated that overexpression of FaMAPK19 improved disease resistance to B. cinerea, but antisense expression of FaMAPK19 caused a reduction in disease resistance. Disease resistance–related transcription factors were almost all upregulated in fruits where FaMAPK19 was overexpressed. These results suggest that FaMAPK19 plays a pivotal role in defense responses in strawberry fruit to B. cinerea. Moreover, we found that the transcript levels of some hormone-related genes, some structural genes, and a series of ripening-related genes were highly influenced by overexpression and antisense expression of FaMAPK19 in fruits, suggesting that FaMAPK19 might also have functions in fruit development and ripening. We thus hypothesize that the FaMAPK19 gene plays a key role in fruit disease resistance as well as a variety of biological functions, including fruit development and ripening regulation.