Studies suggest that SlIDI1 is complexly involved in tomato carotenoid synthesis

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In a recent study, researchers at the Beijing Academy of Agriculture and Forestry and the Chinese Academy of Sciences characterized the molecular mechanism of color formation in orange fruit tomato 3 (oft3), an inbred strain of orange fruit tomato. Using high performance liquid chromatography (HPLC), they found that the carotenoid content of oft3 fruits was significantly reduced and that the β-carotene / lycopene ratio during maturation was high. Further genetic analysis by cross-sectional experiments suggested that oft3 is regulated by a single recessive gene. By bulk separation analysis by high-throughput sequencing (BSA-Seq) and fine mapping combined with genomic sequence analysis, SlIDI1 containing a 116 bp deletion was identified as a candidate gene for the oft3 locus. Functional complementarity and CRISPR-Cas9 knockout experiments confirmed that SlIDI1 is the causative gene.

Next, the authors confirmed that SlIDI1 simultaneously produced both long and short transcripts by selective transcription initiation and alternative splicing. Expression of green fluorescent protein fusion revealed that the long isoform was predominantly localized to the plastid and the N-terminal 59 amino acid extension sequence was involved in its plastid targeting. Short transcripts were identified in leaves and fruits by 5’RACE and in fruits by 3’RACE. Their corresponding proteins lacked transit peptides and / or putative peroxisome targeting sequences, respectively.

It is widely known that IDI1 functions in the MEP pathway upstream of PSY1 and catalyzes the first step of involvement in carotenoid biosynthesis. Interestingly, the authors found that tomatoes carrying the mutated SlIDI1 gene exhibited an orange fruit phenotype rather than the yellow color observed in the r (SlPsy1) mutant. To explain this surprising phenomenon, they found the major carotenoid biosynthetic genes (SlPSY1, SlPDS, SlCRTISO, SlLCY-B1, SlLCY-B2, and SlLCY-E) in two often three-genotype BC1F2 individuals. The expression level of was measured. However, no significant changes were observed in any of these genes compared to expression in wild-type plants. Finally, SlBCH1, which has been reported to encode β-carotene hydroxylase, was found to exhibit transcriptional repression in mutants produced by oft3 and CRISPR-Cas9. Because SLBCH1 catalyzes the conversion of β-carotene to other xanthophylls, the authors found that a decrease in SlBCH1 transcripts delayed β-carotene catabolism, minimized a decrease in β-carotene accumulation, and made Slidi1 It was speculated to contribute to the phenotype of the orange fruit of the mutant. These results suggest that there is a new feedback loop in the carotenoid pathway flux.This study is published in the journal Horticultural research..

The authors say, “SlIDI1 can target multiple organelles through the expression of different isoforms, except whether SlIDI1–5’S and SlIDI1–3’S are derived from the same transcript, and Whether SlIDI1 can target mitochondria or peroxisomes have not yet been confirmed. Further research is needed to address this question. ”

Transcriptional regulatory mechanism of plant pectin biosynthesis

For more information:
Ming Zhou et al, alternative transcription and feedback regulation, suggest that SlIDI1 is involved in tomato carotenoid synthesis in a complex way. Horticultural research (2022). DOI: 10.1093 / hr / uhab045

Provided by Nanjing Agricultural University

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Studies suggest that SlIDI1 is complexly involved in tomato carotenoid synthesis

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