A phospho-switch provided by LRR receptor-like kinase, ALK1/QSK1/KIN7, prioritizes ABCG36/PEN3/PDR8 transport toward defense
biorxiv(2022)
摘要
Based on its proposed substrate preferences, the ABC transporter, ABCG36/PDR8/PEN3, from the model plant Arabidopsis stands at the cross-road between growth and defence. Recently, ABCG36 was shown to export a few indolic compounds, including the auxin precursor, indole-3-butyric acid (IBA), and to be implicated in the export of the major phytoalexin of Arabidopsis, camalexin, although clear-cut proof of camalexin transport activity is still lacking.
Here we provide strong evidence that ABCG36 catalyses the direct, ATP-dependent export of camalexin over the plasma membrane, however, most likely in functional interplay with non-camalexin transporting ABCG isoforms. We identify the leucin-rich repeat receptor-like kinase, Auxin-induced LRR Kinase1 (ALK1/KIN7/QSK1), as a functional kinase to physically interact with and phosphorylate ABCG36. ABCG36 phosphorylation by ALK1 represses unilaterally IBA but not camalexin export leading to a prioritization of ABCG transport toward defense. As a consequence, phospho-dead mutants of ABCG36, like alk1 and abcg36 alleles, are hypersensitive toward infection with the root pathogen, F. oxysporum , caused by elevated fungal progression.
Our findings indicate a novel, direct regulatory circuit between a receptor kinase and an ABC transporter determining transporter substrate specificity. It appears that growth and defense balance decisions in plants are performed on the transporter level by means of a reversible phospho-switch.
### Competing Interest Statement
The authors have declared no competing interest.
* IBA,
: indole-3-butyric acid;
IAA,
: indole-3-acetic acid;
PAT,
: polar auxin transport;
ABCG,
: ATP-binding cassette protein subfamily G;
PDR,
: Pleiotropic drug resistance;
ABCB,
: ATP-binding cassette protein subfamily B;
PIN,
: pin-formed; dag, day(s) after germination;
dai,
: day(s) after infection;
WT,
: wild-type;
MS,
: mass spectrometry.
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关键词
abcg36/pen3/pdr8 transport,phospho-switch,receptor-like
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