Ectopic expression of a BZR1‐1D transcription factor in brassinosteroid signalling enhances carotenoid accumulation and fruit quality attributes in tomato

Abstract

SummaryThe brassinosteroid (BR) response transcription factor Brassinazole resistant 1 (BZR1)-mediated BR signalling regulates many specific developmental processes including fruit ripening. Here, we report the effect of 2,4-epibrassinolide (EBR) and BZR1-1D overexpression on carotenoid accumulation and quality attributes of tomato (Solanum lycopersicum) fruit. EBR-treated pericarp discs of ethylene-insensitive mutant, Never ripe, accumulated significantly more carotenoid than those of the control. The results suggest that BR seems to be involved in modulating pigments accumulation. When three independent transgenic lines overexpressing the Arabidopsis BZR1-1D were used to evaluate the role of BZR1 in regulating tomato fruit carotenoid accumulation and quality attributes, fruits of all three transgenic lines exhibited enhanced carotenoid accumulation and increased soluble solid, soluble sugar and ascorbic acid contents during fruit ripening. In addition, the fruits of two transgenic lines showed dark green shoulder at mature green stage, in accordance with the up-regulated expression level of SlGLK2, which is involved in chloroplast development. Our results indicate the importance of BZR1-centred BR signalling in regulating carotenoid accumulation and quality attributes of tomato fruit and the potential application of the BZR1-like(s) for improvement of nutritional quality and flavour of tomato through genetic engineering.

KNOX genes influence a gradient of fruit chloroplast development through regulation of GOLDEN2‐LIKE expression in tomato

“…Several studies implicate phytohormones in mediating fruit chloroplast development in tomato, and in the case of auxin and BRs enhanced fruit chloroplast development is positively correlated with increased SlGLK expression (Martineau et al ., ; Galpaz et al ., ; Sagar et al ., ; Liu et al ., ). In addition, auxin gradients are involved in several developmental processes, and disruption of auxin signaling in the arf6 / arf8 double mutant results in ectopic KNOX expression and altered floral morphology (Benkova et al ., ; Petersson et al ., ; Tabata et al ., ).…”

DWARF overexpression induces alteration in phytohormone homeostasis, development, architecture and carotenoid accumulation in tomato

“…Significantly, we found that BR levels were closely related to the accumulation of phytoene, phytofluene, β‐carotene and lycopene (Table ). Foliar application of exogenous BRs and ectopic expression of a BZR1‐1D transcription factor in BR signalling could enhance carotenoid accumulation in tomato (Liu et al ., ; Zhu et al ., ). Therefore, BRs are actively involved in the regulation of fruit carotenoid metabolism and manipulation of BR biosynthesis, or their signalling is a potential approach to improve fruit quality in tomato.…”

A critical evaluation of the role of ethylene and MADS transcription factors in the network controlling fleshy fruit ripening

“…) by mutation, gene silencing or knockouts, or overexpression of either the target genes or the individual transcription factors (often ERFs) that regulate them (Grierson, ; M. C. Liu et al ., , ; Xie et al ., ). Ethylene also is effective when applied externally to mature fruit, which provides a very convenient experimental switch, but ripening is probably also influenced by the balance of other hormones including abscisic acid (ABA) (Zhang et al ., ; Ma et al ., ), auxin (Audran‐Delalande et al ., ) and brassinosteroids (L. H. Liu et al ., ).…”