APS and APR gene families in Broussonetia papyrifera: evolutionary conservation, functional divergence, and roles in selenium assimilation and biofortification

Abstract

Selenium (Se) biofortification in forage tree species offers a sustainable strategy to improve nutritional quality. This study investigated the physiological and molecular responses of Broussonetia papyrifera, a high-biomass woody species, to exogenous selenite (Na₂SeO₃) and selenate (Na₂SeO₄). Low Se concentrations (≤ 0.4 mM) significantly enhanced plant growth, while higher concentrations (0.8 mM), especially Na₂SeO₄, inhibited biomass accumulation in a dose-dependent manner. Both forms of Se substantially increased foliar Se content, with Na₂SeO₄ showing higher uptake efficiency. Genome-wide screening identified four sulfate/Na₂SeO₄ assimilation-related genes including ATP sulfurylase 1 (BpAPS1), BpAPS2, adenosine 5′-phosphosulfate reductase (BpAPR1), and BpAPR2. Phylogenetic analyses confirmed the evolutionary conservation of these proteins, which were localized to the chloroplasts. Tissue-specific expression patterns revealed a positive correlation between transcript levels of BpAPS1, BpAPR1, and BpAPR2 and Se content, while BpAPS2 expression was inversely correlated, indicating functional divergence. Compared to wild-type (WT) plants, transgenic Arabidopsis thaliana lines overexpressing these genes accumulated 1.27- to 1.60-fold more Se under Na₂SeO₄ stress, accompanied by coordinated upregulation of key endogenous Se metabolism genes like AtAPS, AtAPR, S-adenosylmethionine carriers 3 (AtSAM), homocysteine S-methyltransferase (AtHMT), methylselenol methyltransferase (AtMMT), suggesting enhanced Se assimilation and detoxification capacity. Collectively, these findings clarify the functional roles of the APS and APR gene families in Se uptake, assimilation, and detoxification in a woody crop, highlighting potential genetic targets for Se biofortification.

Keywords

Broussonetia papyrifera / ATP sulfurylase / Adenosine 5’-phosphate reductase / Selenium biofortification

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Funding

National Natural Science Foundation of China(No.32371929)

Postdoctoral Research Foundation of China(No. 2024MD753913)

Key Research and Development Program of Hubei Province, China (No.2023BBB065)

Supported by the Postdoctoral Fellowship Program of CPSF (GZC20251301)

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The Author(s)