Physiological and transcriptomic analyses reveal novel insights into the cultivar-specific response to alkaline stress in alfalfa (Medicago sativa L.)

Tian-Jiao Wei; Guang Li; Ming-Ming Wang; Yang-Yang Jin; Guo-Hui Zhang; Miao Liu; Hao-Yu Yang; Chang-Jie Jiang; Zheng-Wei Liang

doi:10.1016/j.ecoenv.2021.113017

Physiological and transcriptomic analyses reveal novel insights into the cultivar-specific response to alkaline stress in alfalfa (Medicago sativa L.)

Ecotoxicol Environ Saf. 2021 Nov 22:228:113017. doi: 10.1016/j.ecoenv.2021.113017. Online ahead of print.

Authors

Tian-Jiao Wei¹, Guang Li¹, Ming-Ming Wang², Yang-Yang Jin¹, Guo-Hui Zhang¹, Miao Liu², Hao-Yu Yang², Chang-Jie Jiang³, Zheng-Wei Liang⁴

Affiliations

¹ Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
² Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; Da'an Sodic Land Experiment Station, Da'an, Jilin 131317, China.
³ Institute of Agrobiological Sciences, NARO, Kannondai 2-1-2, Tsukuba 305-8642, Japan. Electronic address: cjjiang@affrc.go.jp.
⁴ Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; Da'an Sodic Land Experiment Station, Da'an, Jilin 131317, China. Electronic address: liangzw@iga.ac.cn.

PMID: 34823214
DOI: 10.1016/j.ecoenv.2021.113017

Abstract

Soil alkalization severely limits plant growth and development, however, the mechanisms of alkaline response in plants remain largely unknown. In this study, we performed physiological and transcriptomic analyses using two alfalfa cultivars (Medicago sativa L.) with different sensitivities to alkaline conditions. The chlorophyll content and shoot fresh mass drastically declined in the alkaline-sensitive cultivar Algonquin (AG) following alkaline treatment (0-25 mM Na₂CO₃ solution), while the alkaline-tolerant cultivar Gongnong NO.1 (GN) maintained relatively stable growth and chlorophyll content. Compared with AG, GN had higher contents of Ca²⁺ and Mg²⁺; the ratios of Ca²⁺ and Mg²⁺ to Na⁺, proline and soluble sugar, as well as higher enzyme activities of peroxidase (POD) and catalase (CAT) under the alkaline conditions. Furthermore, transcriptomic analysis identified three categories of alkaline-responsive differentially expressed genes (DEGs) between the two cultivars: 48 genes commonly induced in both the cultivars (CAR), 574 genes from the tolerant cultivar (TAR), and 493 genes from the sensitive cultivar (SAR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that CAR genes were mostly involved in phenylpropanoid biosynthesis, lipid metabolism, and DNA replication and repair; TAR genes were significantly enriched in metabolic pathways, such as biosynthesis of amino acids and secondary metabolites including flavonoids, and the MAPK signaling pathway; SAR genes were specifically enriched in vitamin B6 metabolism. Taken together, the results identified candidate pathways associated with genetic variation in response to alkaline stress, providing novel insights into the mechanisms underlying alkaline tolerance in alfalfa.

Keywords: Alfalfa; Alkaline stress; Alkaline-responsive genes; Medicago sativa L.; Transcriptomics.