Plants have long evolved a wide array of defense mechanisms activated
through complex signaling pathways. OXI1 kinase is required for activation
of mitogen-activated protein kinases (MAPKs). Furthermore, changes in the
levels of OXI1 appear to be crucial for signaling. Callose deposition also
plays a key role in defense. Newcastle University's Tahsin Shoala led a team
of researchers to prove that OXI1 plays an important role in the defense
against aphids (Myzus persicae).
The Arabidopsis mutant oxi1-2, which has a silenced OXI1, showed significant
resistance both in terms of population build-up and the rate of build-up of
aphids. Meanwhile, callose synthase GSL5 was found to be upregulated in
oxi1-2 in response to aphids.
These results suggest that the aphid resistance in Arabidopsis oxi1-2
mutants is through the induction of callose deposition via MAPKs. A better
understanding of the signaling pathways conferring tolerance to biotic
stress will help future breeding programs for improving crops.