Gibberellin Disrupts Hormonal Homeostasis and Anther Integrity to Trigger Sex Reversal in Spinach

TL;DR

Gibberellin treatment causes male spinach plants to develop female traits, revealing key genes and hormones involved in plant sex determination.

Contribution

Identification of SpAMS as a male-promoting gene and its role in the SpAMS–SpPI pathway in spinach sex determination.

Findings

Gibberellin treatment caused 42% of stamens in male spinach plants to become pistils.

SpAMS activates the B-class gene SpPI and is located in the pseudo-autosomal region of the Y chromosome.

Disruption of SpAMS or SpPGIP leads to carpelization, indicating their role in maintaining male identity.

Abstract

Spinach is a dioecious vegetable and an excellent model for investigating plant sex differentiation. Exogenous gibberellin treatment induced sepal hypoplasia and sex reversal, converting 42% of stamens into pistils in male plants. Transcriptome analysis identified 112 male-biased genes enriched in stamen and pollen development, while hormone profiling revealed coordinated changes in GA, cytokinins, auxin, jasmonic acid, and abscisic acid. Functional assays demonstrated that silencing SpAMS or SpPGIP caused extensive carpelization, and in situ hybridization localized their expression to developing anthers. Dual-luciferase assays confirmed that SpAMS directly activates the B-class gene SpPI, and genomic mapping placed SpAMS in the pseudo-autosomal region of the Y chromosome. These results indicate that GA disrupts hormonal homeostasis and anther wall integrity, while the SpAMS–SpPI pathway regulates tapetal development to maintain male identity. Our findings identify SpAMS as a key male-promoting factor in spinach and provide a framework for elucidating sex determination mechanisms in dioecious plants.

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