SIEVE ELEMENT-LINING CHAPERONE 1 restricts aphid feeding on Arabidopsis during heat stress
Plant Cell. 2017 Sep 28 [Epub ahead of print]
Kloth KJ, Busscher J, Wiegers G, Kruijer W, Buijs G, Meyer RC, Albrectsen BR, Bouwmeester HJ, Dicke M, Jongsma MA
The role of phloem proteins in plant resistance to aphids is still largely elusive. By genome-wide association mapping of aphid behavior on 350 natural Arabidopsis accessions, we identified the small heat shock-like SIEVE ELEMENT-LINING CHAPERONE 1 (SLI1). Detailed behavioral studies on near-isogenic and knockout lines showed that SLI1 impairs phloem feeding. Depending on the haplotype, aphids displayed a different duration of salivation in the phloem. On sli1 mutants, aphids prolonged their feeding sessions and ingested phloem at a higher rate than on wild-type plants. The largest phenotypic effects were observed at 26°C, when SLI1 expression is upregulated. At this moderately high temperature, sli1 mutants suffered from retarded elongation of the inflorescence and impaired silique development. Fluorescent reporter fusions showed that SLI1 is confined to the margins of sieve elements where it lines the parietal layer and co-localizes in spherical bodies around mitochondria. This localization pattern is reminiscent of the clamp-like structures observed in previous ultrastructural studies of the phloem, and shows that the parietal phloem layer plays an important role in plant resistance to aphids and heat stress.
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