Metabolomic homeostasis shifts after callus formation and shoot regeneration in tomato

Abstract

Plants can regenerate from a variety of tissues on culturing in appropriate media. However, the metabolic shifts involved in callus formation and shoot regeneration are largely unknown. The metabolic profiles of callus generated from tomato (Solanum lycopersicum) cotyledons and that of shoot regenerated from callus were compared with the pct1-2 mutant that exhibits enhanced polar auxin transport and the shr mutant that exhibits elevated nitric oxide levels. The transformation from cotyledon to callus involved a major shift in metabolite profiles with denser metabolic networks in the callus. In contrast, the transformation from callus to shoot involved minor changes in the networks. The metabolic networks in pct1-2 and shr mutants were distinct from wild type and were rewired with shifts in endogenous hormones and metabolite interactions. The callus formation was accompanied by a reduction in the levels of metabolites involved in cell wall lignification and cellular immunity. On the contrary, the levels of monoamines were upregulated in the callus and regenerated shoot. The callus formation and shoot regeneration were accompanied by an increase in salicylic acid in wild type and mutants. The transformation to the callus and also to the shoot downregulated LST8 and upregulated TOR transcript levels indicating a putative linkage between metabolic shift and TOR signalling pathway. The network analysis indicates that shift in metabolite profiles during callus formation and shoot regeneration is governed by a complex interaction between metabolites and endogenous hormones.

Metabolite profiling during graft union formation reveals the reprogramming of primary metabolism and the induction of stilbene synthesis at the graft interface in grapevine

“…Some changes in amino acid concentrations between the scion and rootstock stem and graft interface tissues of CS/CS grafts overlap with the metabolome reprogramming of wound induced callus in tomato [29] and induced by the transient over-expression of the WOUND INDUCED DEDIFFERENTIATION1 ( WIND1 ) in oilseed rape [30]. The APETALA2/ethylene response factor transcription factor WIND1 is a key regulator of wound-induced cellular reprogramming in Arabidopsis [31].…”

“…The APETALA2/ethylene response factor transcription factor WIND1 is a key regulator of wound-induced cellular reprogramming in Arabidopsis [31]. Tomato calli [29], the transient over-expression of WIND1 [30], and the graft interface of grapevine are characterized by significantly higher concentrations of Gln and GABA, as well as increase of Ala, Val and Ile. This suggests that metabolome reprogramming in response to wound callus formation is similar between herbaceous and woody species, although the orthologue of WIND1 in grapevine was not differentially expressed between the rootstock and graft interface tissues [21] and some amino acids show opposite responses.…”

“…This suggests that metabolome reprogramming in response to wound callus formation is similar between herbaceous and woody species, although the orthologue of WIND1 in grapevine was not differentially expressed between the rootstock and graft interface tissues [21] and some amino acids show opposite responses. For example, Lys, Thr, and Phe accumulate in the callus cells of tomato relative to cotyledons [29], whereas they are in lower concentrations at the graft interface of grapevine in comparison to the surrounding woody stem tissues. Similarly, Pro, Ser, Asp and Gly accumulate in the callus tissues of tomato [29], but their concentration is not different between the stem and graft interface tissue of grapevine.…”

“…For example, Lys, Thr, and Phe accumulate in the callus cells of tomato relative to cotyledons [29], whereas they are in lower concentrations at the graft interface of grapevine in comparison to the surrounding woody stem tissues. Similarly, Pro, Ser, Asp and Gly accumulate in the callus tissues of tomato [29], but their concentration is not different between the stem and graft interface tissue of grapevine.…”

Temporal and Spatial Expression Analysis of Shoot-Regeneration Regulatory Genes during the Adventitious Shoot Formation in Hypocotyl and Cotyledon Explants of Tomato (CV. Micro-Tom)

“…Zuiken and cv. Ailsa Crai) was tested in 1 mg L −1 Zeatin, 0.1 mg L −1 IAA, and 3% sucrose [32,33]. In this study, the optimal culture conditions for adventitious shoot formation from cotyledon explants of tomato (cv.…”