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The enigma of environmental pH sensing in plants


Environmental pH is a critical parameter for innumerable chemical reactions, myriad biological processes and all forms of life. The mechanisms that underlie the perception of external pH (pHe) have been elucidated in detail for bacteria, fungi and mammalian cells; however, little information is available on whether and, if so, how pHe is perceived by plants. This is particularly surprising since hydrogen ion activity of the substrate is of paramount significance for plants, governing the availability of mineral nutrients, the structure of the soil microbiome and the composition of natural plant communities. Rapid changes in soil pH require constant readjustment of nutrient acquisition strategies, which is associated with dynamic alterations in gene expression. Referring to observations made in diverse experimental set-ups that unambiguously show that pHe per se affects gene expression, we hypothesize that sensing of pHe in plants is mandatory to prioritize responses to various simultaneously received environmental cues.

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Fig. 1: Factors that determine soil pH and effects of soil pH on plants.
Fig. 2: pH sensing in bacteria.
Fig. 3: pH sensing in eukaryotes.
Fig. 4: Acid-activated KIR channels in plants.
Fig. 5: Environmental pH modulates the biosynthesis of catecholic coumarins.
Fig. 6: Signature pH values of plant organelles.


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Research in the Schmidt Laboratory is funded by Academia Sinica and the Ministry of Science and Technology (MOST).

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H.-H.T. conducted research that led to the hypothesis put forward in the manuscript, composed the figures and contributed to the writing. W.S. initiated the research and wrote the paper.

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Correspondence to Wolfgang Schmidt.

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Tsai, HH., Schmidt, W. The enigma of environmental pH sensing in plants. Nat. Plants 7, 106–115 (2021).

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