Effect of water availability on changes in root amino acids and associated rhizosphere on root exudation of amino acids in Pisum sativum L. (May 2019)

• Record Type: Journal Article
• Authors: Bobille, Hélène; Fustec, Joëlle; Robins, Richard J.; Cukier, Caroline; Limami, Anis M.
• Is Part Of: Phytochemistry. Volume 161(2019)
• Page Start: 75
• Page End: 85
• Publication Date: 2019-05
• Subjects: Pisum sativum L. -- Leguminoseae -- Amino acids -- Water stress -- Rhizosphere -- CG-MS -- 15N-labelling; AA amino acid -- DAS days after sowing -- DW dry weight -- GABA γ-amino-butyric acid -- HSer homoserine -- MWHC maximum water holding capacity -- PGPR plant growth-promoting rhizobacteria -- WD water deficit; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2019.01.015
• Languages: English
• ISSNs: 0031-9422

Abstract

Abstract: Root exudation is considered to regulate the abundance of the microbial community. It may vary both qualitatively and quantitatively in response to the environment in which the plant is growing. A part of exuded N derives from amino acids (AAs). This, in turn, may help plants to cope with abiotic stresses by favouring positive interactions with the rhizosphere environment, thus playing a potential role in maintaining healthy plants. In this respect, an under-investigated area is the effect of stress due to water deficit (WD). It is proposed that the AA profile in the rhizosphere may be altered by WD, reflecting a modulation of root AA exudation linked to a physiological response of the plant to water stress. To investigate this, Pisum sativum L. plants, grown in unsterilised Rhizobium leguminosarum- enriched soil, were stem-labelled with 15 N-urea for 96 h, and then subjected/not subjected to 72 h of WD. The concentrations and abundance of 15 N-labelling in individual AAs were determined in both roots and the associated rhizosphere at 24, 48 and 72 h after stress application. It was found that both AAs metabolism in the pea root and AAs exudation were strongly modified in WD conditions. After 24 h of WD, the concentrations of all measured AAs increased in the roots, accompanied by a dramatic stress-related increase in the 15 N-labelling of some AAs. Furthermore, after 48–72 h of WD, the concentrations of Pro, Ala and Glu increased significantly within the rhizosphere, notably with a concomitant increase in 15 N-enrichment in Pro, Ser, Asn, Asp, Thr and Ile. These results support the concept that, in response to WD, substantial amounts of recently assimilated N are rapidly translocated from the shoots to the roots, a portion of which is exuded as AAs. This leads to the rhizosphere being relatively augmented by specific AAs (notably HSer, Pro and Ala) in WD conditions, with a potential impact on soil water retention. Graphical abstract: Image 1 Highlights: 15 N labelled pea plants grown in unsterilised soil were subjected or not to 72 h of water deficit. After 24 h of stress, AA concentrations in the roots and 15 N-labelling of some AAs increased. After 48 h, the concentrations of Pro and Glu increased significantly within the rhizosphere. A concomitant and notable increase in 15 N-enrichment in Hser, Glu, Ala, Pro and Asn was observed. Under water stress, recently assimilated N is translocated to the roots and AAs are increasingly released into the soil.