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bioRxiv · 10.1101/839308

An rpw8 quadruple mutant of Arabidopsis Col-0 is partially compromised in bacterial and fungal resistance

Castel, B.·Wu, Y.·Xiao, S.·Jones, J. D.
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Abstract

The plant immune system relies on both cell-surface and intracellular NLR (nucleotide-binding, leucine-rich repeat) receptors. NLRs respond to pathogen effectors and activate effector-triggered immunity: a cocktail of responses, often accompanied by cell death, resulting in resistance. RPW8 encodes an unusual non-NLR Resistance (R) protein and confers broad-spectrum powdery mildew resistance. It requires genetic components also required by some NLRs, resembles the HeLo-containing protein MLKL (necroptosis executor in animals) and HET-S (cell death executor in fungi) and is targeted to the extra-haustorial membrane during powdery mildew infection by its N-terminal non-cleaved signal anchor domain. RPW8 displays extensive recent duplication events in Arabidopsis and certain alleles can induce oligomerisation-dependent activation of the NLR RPP7. All these features enabled us to formulate hypotheses for RPW8 function: (1) RPW8 could be a cell death executor for defence against pathogens. (2) RPW8 could be a decoy for effector targets. To test these hypotheses, we generated a quadruple knock-out mutant of the four RPW8-homologous copies in Arabidopsis Col-0, using CRISPR. The mutant still displays cell death upon activation of four well-characterised NLRs. However, it is partially impaired in powdery mildew resistance and also in bacterial resistance. Interestingly Col-0_rpw8 is delayed in flowering transition. In conclusion, RPW8 plays a broad role in immunity and plant development, beyond resistance to powdery mildew. There is no evidence that it is involved in executing ETI-associated cell death.

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Castel, B., Wu, Y., Xiao, S., Jones, J. D.. 2019-11-12. An rpw8 quadruple mutant of Arabidopsis Col-0 is partially compromised in bacterial and fungal resistance. https://doi.org/10.1101/839308

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