The Papaya Transcription Factor CpNAC1 Modulates Carotenoid Biosynthesis through Activating Phytoene Desaturase Genes CpPDS2/4 during Fruit Ripening

Abstract

Papaya fruits accumulate carotenoids during fruit ripening. Although many papaya carotenoid biosynthesis pathway genes have been identified, the transcriptional regulators of these genes have not been characterized. In this study, a NAC transcription factor, designated as CpNAC1, was characterized from papaya fruit. CpNAC1 was localized exclusively in nucleus and possessed transcriptional activation activity. Expression of carotenoid biosynthesis genes phytoene desaturases (CpPDSs) and CpNAC1 was increased during fruit ripening and by propylene treatment, which correlates well with the elevated carotenoid content in papaya. The gel mobility shift assays and transient expression analyses demonstrated that CpNAC1 directly binds to the NAC binding site (NACBS) motifs in CpPDS2/4 promoters and activates them. Collectively, these data suggest that CpNAC1 may act as a positive regulator of carotenoid biosynthesis during papaya fruit ripening possibly via transcriptional activation of CpPDSs such as CpPDS2/4.

An R2R3‐MYB transcription factor represses the transformation of α‐ and β‐branch carotenoids by negatively regulating expression of CrBCH2 and CrNCED5 in flavedo of Citrus reticulate

“…All these TFs regulate the expression of the genes that contribute only to the early steps of lycopene biosynthesis. The TFs that directly regulate the expression of genes responsible for the transformation of α‐ and β‐branch carotenoids remain unknown (Toledoortiz et al ., ; Martel et al ., ; Fu et al ., ). In MT, we observed an inverse correlation in the expression of CrMYB68 and CrBCH2 (Fig.…”

“…During seedling development in Arabidopsis thaliana, phytochrome-interacting factor 1 (PIF1) was reported to directly repress the expression of the PSY gene (Toledoortiz et al, 2010). Moreover, a MADS-box TF named RIPENING INHIBITOR (RIN) in Solanum lycopersicum and a NAM/ATAF1/2/CUC2 (NAC) TF named CpNAC1 in Carica papaya L. were reported to directly induce the expression of SlPSY and CpPDS2/4, respectively (Martel et al, 2011;Fu et al, 2016). All of these TFs regulate lycopene biosynthesis, while the TFs that directly regulate the aand b-branches of carotenoid metabolism remain unknown.…”

Photo-Oxidative Stress during Leaf, Flower and Fruit Development

“…A lot of attention has been paid to the biosynthetic mechanisms underlying carotenoid accumulation in the chromoplasts of flowers (Kishimoto and Ohmiya, 2006;Chiou et al, 2010) and fruits (Fraser et al, 1994;Kato et al, 2004;Fu et al, 2016), mainly because of consumer tastes. Moreover, there have been several projects to enhance carotenoid accumulation in food products by genetic engineering to overcome typical dietary diseases associated with carotenoid deficiency in developing countries (Ye et al, 2000;Diretto et al, 2007).…”

Shotgun proteomics of peach fruit reveals major metabolic pathways associated to ripening

“…Their identi cation could help to uncover the transcription regulation that underlies the extensive changes triggered by fruit ripening. TFs associated to ripening in climacteric fruit have been identi ed in apricot [93,94], melon [95], banana [96,97], tomato [98,99], papaya [100,101,102], among others. By 2015, around 1,533 TFs were identi ed in P. persica [20], however just a few have been characterized and even less have been associated to the fruit ripening process.…”