Chilling-responsive strigolactone signaling orchestrates bud break and chilling tolerance in apple.
Zhang Y, Zhu Y, Wang C, Ge H, Guo K
Plant Signaling
Those 'chilling hours' on apple nursery tags — the reason you can't grow a Honeycrisp reliably in coastal California — now have a molecular explanation, and it may reshape how breeders design varieties for warming or unusually harsh winters.
Apple trees need a set amount of cold weather each winter to 'wake up' and bloom in spring. Scientists found a hormone that acts like a dial: the right amount of cold nudges the tree toward budding, but too much cold causes the tree to shift its energy toward cold survival instead — leaving it reluctant to flower even when warm weather arrives. This tug-of-war between 'stay protected' and 'wake up' determines which climates apple trees can actually thrive in.
Key Findings
Strigolactone hormones serve a dual role in apple trees — suppressing bud break while simultaneously boosting tolerance to prolonged cold stress, with a single protein (D53) acting as the central switch between these two states.
During normal chilling, cold temperatures activate transcription factors (CBF4 and TCP14) that build up D53 protein, driving bud break competence; as chilling accumulates further, rising strigolactones accelerate D53 breakdown to prioritize cold survival over dormancy release.
Under excessive chilling, elevated strigolactones trigger a phosphorylation cascade that frees the ICE1 protein from D53, activating cold-stress genes at the expense of bud break capacity — a molecular explanation for why orchards in extreme-cold regions show weakened spring flowering.
chevron_right Technical Summary
Scientists discovered that a plant hormone called strigolactone acts as a molecular switch in apple trees, balancing the competing needs to break winter dormancy and survive prolonged cold. This mechanism explains why apple trees grown in regions with excessively long winters lose the ability to bud out reliably in spring, defining the geographic limits of apple cultivation.
Abstract Preview
Temperature is a critical factor governing apple (Malus domestica) cultivation. Adequate chilling exposure promotes bud dormancy release, but prolonged chilling induces crop damage. However, the me...
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An apple is the round, edible fruit of an apple tree. Fruit trees of the orchard or domestic apple, the most widely grown in the genus, are cultivated worldwide. The tree originated in Central Asia, where its wild ancestor, Malus sieversii, is still found. Apples have been grown for thousands of ...