Effects of bisphenol A on chlorophyll synthesis in soybean seedlings

Bisphenol A (BPA), as an emerging environmental pollutant, is potentially harmful to plant growth. Chlorophyll (Chl) is critical in photosynthesis that provides matter and energy for plant growth. How BPA affects the chlorophyll content remains largely unknown. Here, the effects of BPA on Chl synthesis in soybean seedlings were investigated. Exposure to 1.5 mg/L BPA decreased the 5-aminolevulinic acid (ALA) content and increased protoporphyrin IX (Proto IX), magnesium protoporphyrin, and protochlorophyll contents and 5-aminolaevulinic acid dehydratase, porphobilinogen deaminase, uroporphyrinogen III synthase, uroporphyrinogen III decarboxylase, and protoporphyrinogen oxidase activities. Exposure to 17.2 and 50.0 mg/L BPA exerted the opposite effects on these four intermediates and five enzymes. Following the withdrawal of BPA exposure, the aforementioned parameters gradually recovered, except magnesium protoporphyrin content in exposure to 50.0 mg/L BPA. Our findings revealed that exposure to low-concentration BPA increased the Chl content in soybean seedlings through improving Chl synthesis, especially the conversion from ALA to Proto IX, whereas exposure to high-concentration BPA decreased the Chl content through inhibiting Chl synthesis, especially the conversion from ALA to Proto IX. The dual effects of BPA were largely reversed following the withdrawal of BPA exposure.