Citric acid-mediated abiotic stress tolerance in plants

Authors: TAHJIB-UL-ARIF, MD - Okayama University; ZAHAN, MST. ISHRAT - Non ARS Employee; KARIM, MD. MASUDUL - Bangladesh Agricultural University; IMRAN, SHAHIN - Khulna Agricultural University; Hunter, Charles; ISLAM, MD.SAIFUL - Bangamata Sheikh Fojilatunnesa Mujib Science & Technology University; MIA, MD.ASHIK - Bangladesh Agricultural University; HANNAN, MD. ABDUL - Bangladesh Agricultural University; RHAMAN, MOHAMMAD - Bangamata Sheikh Fojilatunnesa Mujib Science & Technology University; HOSSAIN, M. AFZAL - Bangladesh Agricultural University; BRESTIC, MARIAN - Bangladesh Agricultural University; SKALICKY, MILAN - Czech University Of Life Sciences Prague; MURATA, YOSHIYUKI - Okayama University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2021
Publication Date: 7/5/2021
Citation: Tahjib-Ul-Arif, M.; Zahan, M.; Karim, M.; Imran, S.; Hunter, C.T.; Islam, M.; Mia, M.; Hannan, M.; Rhaman, M.S.; Hossain, M.; Brestic, M.; Skalicky, M.; Murata, Y. 2021. Citric acid-mediated abiotic stress tolerance in plants. International Journal of Molecular Sciences. 22(13): 7235. http://doi.org/10.3390/ijms22137235.
DOI: https://doi.org/10.3390/ijms22137235

Interpretive Summary: Due to its stabilizing influence on plants, treatment of crops with citric acid (CA) has become an important tool for combating decreased yield loss due to environmental stresses. This review article summarizes our current understanding of CA-mediated stress tolerance in plants. Generally, CA application relieves environmental stresses (drought, cold, heat, salinity, and heavy metal) by altering physiological and metabolic responses in plants. CA occupies an important position in central metabolism in plants. By boosting endogenous CA with exogenous application, metabolic pathways for certain osmotic regulators, stress response hormones, and secondary metabolites are up-regulated that promote stress tolerance. CA also functions in heavy metal (HM) stress tolerance by acting as a HM chelator, preventing HM uptake and promoting HM sequestration. This review also highlights areas where additional research on the mechanisms of CA-induced stress tolerance is needed. Collating and disseminating the knowledge may inspire other research programs to further investigate or incorporate CA into their studies.

Technical Abstract: Several recent studies have shown that citric acid/citrate (CA) can confer abiotic stress tolerance to plants. Exogenous CA application leads to improved growth and yield in crop plants under various abiotic stress conditions. Improved physiological outcomes are associated with higher photo-synthetic rates, reduced reactive oxygen species, and better osmoregulation. Application of CA also induces antioxidant defense systems, promotes increased chlorophyll content, and effects secondary metabolism to limit plant growth restrictions under stress. In particular, CA has a major impact on relieving heavy metal stress by promoting precipitation, chelation, and sequestration of metal ions. This review summarizes the mechanisms that mediate CA-regulated changes in plants, primarily CA’s involvement in the control of physiological and molecular processes in plants under abiotic stress conditions. We also review genetic engineering strategies for CA-mediated abiotic stress tolerance. Finally, we propose a model to explain how CA’s position in complex metabolic networks involving the biosynthesis of phytohormones, amino acids, signaling mol-ecules, and other secondary metabolites could explain some of its abiotic stress-ameliorating properties. This review summarizes our current understanding of CA-mediated abiotic stress tolerance and highlights areas where additional research is needed.