Synergy of arbuscular mycorrhizal symbiosis and\xa0exogenous Ca2+ benefits peanut (Arachis hypogaea L.) growth through the shared hormone and flavonoid pathway

Li Cui,Xinguo Li,Yun Geng,JingJing Meng,Shubo Wan,Feng Guo,Jialei Zhang,Sha Yang

doi:10.1038/s41598-019-52630-7

Abstract

Peanut yield is severely affected by exchangeable calcium ion (Ca2+) deficiency in the soil. Arbuscular mycorrhizal (AM) symbiosis increases the absorption of Ca2+ for host plants. Here, we analyzed the physiological and transcriptional changes in the roots of Arachis hypogaea L. colonized by Funneliformismosseae under Ca2+-deficient and -sufficient conditions. The results showed that exogenous Ca2+ application increased arbuscular mycorrhizal fungi (AMF) colonization, plant dry weight, and Ca content of AM plants. Simultaneously, transcriptome analysis showed that Ca2+ application further induced 74.5% of differentially expressed gene transcripts in roots of AM peanut seedlings. These genes are involved in AM symbiosis development, hormone biosynthesis and signal transduction, and carotenoid and flavonoid biosynthesis. The transcripts of AM-specific marker genes in AM plants with Ca2+ deprivation were further up-regulated by Ca2+ application. Gibberellic acid (GA3) and flavonoid contents were higher in roots of AM- and Ca2+-treated plants, but salicylic acid (SA) and carotenoid contents specifically increased in roots of the AM plants. Thus, these results suggest that the synergy of AM symbiosis and Ca2+ improves plant growth due to the shared GA- and flavonoid-mediated pathway, whereas SA and carotenoid biosynthesis in peanut roots are specific to AM symbiosis.

Highlights

Peanut yield is severely affected by exchangeable calcium ion (Ca2+) deficiency in the soil
The quantification of arbuscular mycorrhizal fungi (AMF) colonization showed that 60.33% and 80.67% of plant roots were inoculated by F. mosseae under both Ca2+-deficient and Ca2+sufficient conditions, respectively (Fig. 1A), indicating that Ca2+ application could significantly improve the number of fungal colonizers
304 differentially expressed genes (DEGs) were shared by Ca0 + Arbuscular mycorrhizal (AM), Ca6 − AM, and Ca6 + AM plants and the number of DEGs gradually increased in the plants (Fig. 2B), indicating that AM symbiosis combined with exogenous Ca2+ induced more transcriptional changes

Summary

Introduction

Peanut yield is severely affected by exchangeable calcium ion (Ca2+) deficiency in the soil. Transcriptome analysis showed that Ca2+ application further induced 74.5% of differentially expressed gene transcripts in roots of AM peanut seedlings These genes are involved in AM symbiosis development, hormone biosynthesis and signal transduction, and carotenoid and flavonoid biosynthesis. In the process of establishing the AM symbiosis, many AM-specific marker genes must be initiated by Ca2+ concentration change[14], such as RAM1 (REDUCED ARBUSCULAR MYCORRHIZA 1), RAM2 (glycerol-3-phosphate acetyltransferase), CCD1 (carotenoid cleavage dioxygenase), PT1 (phosphate transporter), and DELLA15–17. These findings suggest that Ca2+ plays an important role in AM development. Increases in flavonoid and anthocyanin were considered to be indispensable in regulating the establishment of AM symbiosis[22,23]

Methods

Results

Conclusion