Effects of exogenous calcium on the drought response of the tea plant (Camellia sinensis (L.) Kuntze)

Lyudmila S Malyukova; Natalia G Koninskaya; Yuriy L Orlov; Lidiia S Samarina

doi:10.7717/peerj.13997

Effects of exogenous calcium on the drought response of the tea plant (Camellia sinensis (L.) Kuntze)

PeerJ. 2022 Aug 29:10:e13997. doi: 10.7717/peerj.13997. eCollection 2022.

Authors

Lyudmila S Malyukova¹, Natalia G Koninskaya¹, Yuriy L Orlov^{2

3}, Lidiia S Samarina^{1

4}

Affiliations

¹ Federal Research Centre the Subtropical Scientific Centre of the Russian Academy of Sciences, Sochi, Russia.
² Agrarian and Technological Institute, Peoples' Friendship University of Russia, Moscow, Russia.
³ Digital Health Institute, I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), Moscow, Russia.
⁴ Center of Genetics and Life Sciences, Sirius University of Science and Technology, Sochi, Russia.

Abstract

Background: Drought is one of the major factors reducing the yield of many crops worldwide, including the tea crop (Camellia sinensis (L.) Kuntze). Calcium participates in most of cellular signaling processes, and its important role in stress detection and triggering a response has been shown in many crops. The aim of this study was to evaluate possible effects of calcium on the tea plant response to drought.

Methods: Experiments were conducted using 3-year-old potted tea plants of the best local cultivar Kolkhida. Application of ammonium nitrate (control treatment) or calcium nitrate (Ca treatment) to the soil was performed before drought induction. Next, a 7-day drought was induced in both groups of plants. The following physiological parameters were measured: relative electrical conductivity, pH of cell sap, and concentrations of cations, sugars, and amino acids. In addition, relative expression levels of 40 stress-related and crop quality-related genes were analyzed.

Results: Under drought stress, leaf electrolyte leakage differed significantly, indicating greater damage to cell membranes in control plants than in Ca-treated plants. Calcium application resulted in greater pH of cell sap; higher accumulation of tyrosine, methionine, and valine; and a greater Mg²⁺ content as compared to control plants. Drought stress downregulated most of the quality-related genes in both groups of tea plants. By contrast, significant upregulation of some genes was observed, namely CRK45, NAC26, TPS11, LOX1, LOX6, Hydrolase22, DREB26, SWEET2, GS, ADC, DHN2, GOLS1, GOLS3, and RHL41. Among them, three genes (LOX1, RHL41, and GOLS1) showed 2-3 times greater expression in Ca-treated plants than in control plants. Based on these results, it can be speculated that calcium affects galactinol biosynthesis and participates in the regulation of stomatal aperture not only through activation of abscisic-acid signaling but also through jasmonic-acid pathway activation. These findings clarify calcium-mediated mechanisms of drought defense in tree crops. Thus, calcium improves the drought response in the tea tree.

Keywords: Drought stress; Exogenous calcium; Plant physiology; Plant transcription factors; Tea plant.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Calcium / metabolism
Camellia sinensis* / genetics
Droughts
Tea / metabolism

Substances

Calcium
Tea

Grants and funding

This study was financially supported by the Russian Foundation for Basic Research and the Administration of the Krasnodar Territory, Grant No. 19-416-230049. The genes search and primers design for this study were funded by Russian Science Foundation (grant #18-76-10001, https://rscf.ru/project/21-76-03003/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.