Distinct thresholds condition sense PTGS initiation and amplification.

Lacroix, M.; Butel, N.; Barrios, A.; Yu, A.; Bouteiller, N.; Le Masson, I.; Vaucheret, H.

doi:10.64898/2026.05.05.722629

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bioRxiv · 10.64898/2026.05.05.722629

Distinct thresholds condition sense PTGS initiation and amplification.

Lacroix, M.·Butel, N.·Barrios, A.·Yu, A.·Bouteiller, N.·Le Masson, I.·Vaucheret, H.

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Abstract

It has long been known that Pro35S-driven sense transgenes have a high propensity to undergo post-transcriptional gene silencing (S-PTGS). However, what exactly conditions S-PTGS initiation and amplification to make it systemic remains unknown. Through genetic screens, we show that antagonistic chromatin-related mutations enhancing and reducing transgene expression, result in enhanced and reduced S-PTGS amplification capacities, respectively, without affecting the initiation rate. Analysis of a large set of independent transgenic plants confirm a direct relationship between transgene expression and its capacity to amplify S-PTGS. Combining an inducible or a tissue-specifically expressed GUS transgene with a Pro35S:GUS transgene locus prone to amplify S-PTGS but unable to spontaneously initiate it induces systemic S-PTGS, indicating that transient and/or local passing of a discrete threshold is sufficient to initiate S-PTGS. Together, these results call for the existence of distinct thresholds related to transiently produced aberrant RNA and permanently produced target mRNA levels, which condition S-PTGS initiation and amplification, respectively. We show that this model also applies to endogenous genes for which RNA Quality Control (RQC) acts as a first layer of protection against S-PTGS, and DCL2s obscuration by DCL4 as a second layer, allowing RQC to dysfunction locally without translating into the drama of systemic S-PTGS.

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Lacroix, M., Butel, N., Barrios, A., Yu, A., Bouteiller, N., Le Masson, I., Vaucheret, H.. 2026-05-07. Distinct thresholds condition sense PTGS initiation and amplification.. https://doi.org/10.64898/2026.05.05.722629

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