Transcriptome profiling reveals the roles of pigment mechanisms in postharvest broccoli yellowing

Abstract

Postharvest broccoli is prone to yellowing during storage, which is the key factor leading to a reduction in value. To explore appropriate control methods, it is important to understand the mechanisms of yellowing. We analyzed the genes related to the metabolism of chlorophyll, carotenoids, and flavonoids and the transcription factors (TFs) involved in broccoli yellowing using transcriptome sequencing profiling. Broccoli stored at 10 °C showed slight yellowing on postharvest day 5 and serious symptoms on day 12. There were significant changes in chlorophyll fluorescence kinetics, mainly manifesting as a decrease in the Fv/Fm value and an increase in nonphotochemical quenching, during the yellowing process. Transcriptome sequencing profiles from samples of fresh broccoli and broccoli with slight and severe yellowing revealed 6, 5, and 4 differentially expressed genes involved in chlorophyll metabolism, carotenoid biosynthesis, and flavonoid biosynthesis, respectively. The transcription factor gene ontology categories showed that the MYB, bHLH, and bZip gene families were involved in chlorophyll metabolism. In addition, the transcription factor families included NACs and ethylene response factors (ERFs) that regulated carotenoid biosynthesis. Reverse transcription polymerase chain reaction further confirmed that bHLH66, PIF4, LOB13, NAC92, and APL were vital transcription factors that potentially regulated the CAO and HYD genes and were involved in chlorophyll metabolism and the carotenoid biosynthetic process. The flavonoid biosynthetic pathway was mainly regulated by MYBs, NACs, WRKYs, MADSs, and bZips. The results of the differentially expressed gene (DEG) and pigment content analyses indicated that the transcriptome data were accurately and positively associated with broccoli yellowing.

Low temperature modulates natural peel degreening in lemon fruit independently of endogenous ethylene

“…Various TFs in Arabidopsis such as NACs (AtNAC046 and AtORE1), bHLHs (AtPIF4 and AtPIF5), and ethylene insensitive 3 (AtEIN3) have been shown to significantly enhance leaf senescence by promoting the activity of genes related to chlorophyll degradation ( Song et al , 2014 ; Qiu et al , 2015 ; Zhang et al , 2015 ; Oda-Yamamizo et al , 2016 ). In broccoli ( Brassica oleracea ), the MYB, bHLH, and bZIP gene families are associated with chlorophyll metabolism while NACs and ERFs regulate carotenoid biosynthesis ( Luo et al , 2019 ). CitERF6 and CitERF13 have also been associated with chlorophyll degradation during ethylene-induced and natural peel degreening in citrus ( Yin et al , 2016 ; Li et al , 2019 ).…”

Transcriptional regulation of bark freezing tolerance in apple (Malus domestica Borkh.)

“…HTSeq v0.5.4p3 was used to count the number of reads mapped to each gene or exon region 73 . The read counts for each gene were normalized by the FPKM 74 (fragments per kilobase of transcript per million mapped reads) method, which is often used for estimating gene expression levels. To reveal the variations in the datasets between the chilling and freezing stress levels, a cutoff of FPKM ≥ 0.01 was selected to define potentially meaningful gene expression.…”

Integrated analysis of the metabolome and transcriptome in different developmental stages of Cerasus humilis peel coloration

“…Studies of C. humilis fruit color have revealed that in addition to DEGs, TFs play a key role in the regulation of color changes and the activity of pigment biosynthetic pathways [35]. MYB TFs contribute to the regulation of plant secondary metabolism, including anthocyanin biosynthesis [26,36].…”