Pivotal roles of ELONGATED HYPOCOTYL5 in regulation of plant development and fruit metabolism in tomato

Abstract

The transcription factor ELONGATED HYPOCOTYL5 (HY5) plays critical roles in plant photomorphogenesis. Previous studies on HY5 have mainly focused on the seedling stage in Arabidopsis (Arabidopsis thaliana), and its functions in other plant species have not been well characterized, particularly at adult stages of development. In this report, we investigated the functions of tomato (Solanum lycopersicum) HY5 (SlHY5) from seedlings to adult plants with a focus on fruits. Genome-edited slhy5 mutants exhibited typical compromised photomorphogenesis in response to various light conditions. The slhy5 mutants showed reduced primary root length and secondary root number, which is associated with altered auxin signaling. SlHY5 promoted chlorophyll biosynthesis from seedling to adult stages. Notably, the promotive role of SlHY5 on chlorophyll accumulation was more pronounced on the illuminated side of green fruits than on their shaded side. Consistent with this light-dependent effect, we determined that SlHY5 protein is stabilized by light. Transcriptome and metabolome analyses in fruits revealed that SlHY5 has major functions in the regulation of metabolism, including the biosynthesis of phenylpropanoids and steroidal glycoalkaloids. These data demonstrate that SlHY5 performs both shared and distinct functions in relation to its Arabidopsis counterpart. The manipulation of SlHY5 represents a powerful tool to influence the two vital agricultural traits of seedling fitness and fruit quality in tomato.

Evaluation of the effects of ripening-related genes on fruit metabolites and the associated regulatory mechanisms in tomato

“…Moreover, the chalcone synthase ( CHS1 ), CHS2 , flavanone 3-hydroxylase ( F3H ), and flavonol synthase ( FLS1 ) expression levels decreased significantly (Fig. 5C), indicating that HY5 may regulate the expression of biosynthetic genes to control flavonoid accumulation (Zhang et al, 2022). Of the 85 differentially accumulated flavonoids, 81 were significantly less abundant in ap2a-cr1 than in the WT, including 12 metabolites related to flavonoid biosynthesis.…”

“…In the Slhy5 mutant, the fruit exhibit delayed ripening, have a relatively low chlorophyll content during the mature green fruit stage, and appear light red in the final ripening stage. Metabolome and transcriptome analyses of the fruit indicated that HY5 positively regulates the accumulation of flavonoids and caffeoylquinic acid (Zhang et al, 2022). The NOR-like1 gene, which encodes a TF belonging to the NAC family, is a newly identified positive regulator of tomato fruit ripening.…”

Targeting editing of tomatoSPEECHLESScis-regulatory regions generates plants with altered stomatal density in response to changing climate conditions

“…Line #10, a relatively small deletion which exhibits a dampened light response, interrupts one of the A-boxes (Figure 1c and S1e). Future experiments may reveal the roles of tomato HY5 and PIF genes (40, 41) in stomatal regulation. It will be particularly interesting to find that HY5 is a direct transcriptional regulator of SlSPCH because in Arabidopsis, there is an intermediary between HY5 and regulation of SPCH protein (4).…”

Light regulation of the biosynthesis of phenolics, terpenoids, and alkaloids in plants

“…While the biosynthesis and regulation of these SM by the phytohormone jasmonate acid (JA) have been a major focus of many studies 112 , recent research has highlighted the regulatory roles of light in the biosynthesis of GSLs 113 , alkaloids including vindoline in C. roseus 114 , camptothecin in Camptotheca acuminata (Chinese Happy Tree) 115 , and SGAs in tomato (Fig. 1 ) 116 .…”

“…SGA biosynthesis is light inducible as most of the GAMEs are upregulated in response to light exposure 126 . The core light signaling components, including the activator SlHY5 116 , 126 and the repressor SlPIF3 126 , regulate SGA biosynthesis. Specifically, SlHY5 directly activates the genes encoding GAME1, GAME4, and GAME17, while SlPIF3 acts as a repressor (Fig.…”