Peptide signaling for drought-induced tomato flower drop

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Science  27 Mar 2020:
Vol. 367, Issue 6485, pp. 1482-1485
DOI: 10.1126/science.aaz5641

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Fruit abscission in response to drought

Plants faced with drought, or simply not quite enough water, may be more likely to drop their fruit prematurely. Reichardt et al. found that a small signaling peptide hormone, phytosulfokine, which was previously known for its ability to regulate plant cell growth, also drives fruit abscission. Processed, and thus activated, by a subtilisin-like protease, phytosulfokine in turn drives expression of the hydrolases that degrade the cell walls in the abscission zone, leading to dropped fruit.

Science, this issue p. 1482


The premature abscission of flowers and fruits limits crop yield under environmental stress. Drought-induced flower drop in tomato plants was found to be regulated by phytosulfokine (PSK), a peptide hormone previously known for its growth-promoting and immune-modulating activities. PSK formation in response to drought stress depends on phytaspase 2, a subtilisin-like protease of the phytaspase subtype that generates the peptide hormone by aspartate-specific processing of the PSK precursor in the tomato flower pedicel. The mature peptide acts in the abscission zone where it induces expression of cell wall hydrolases that execute the abscission process. Our results provide insight into the molecular control of abscission as regulated by proteolytic processing to generate a small plant peptide hormone.

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