Transcriptional Regulation of Carotenoid Biosynthesis in Plants: So Many Regulators, So Little Consensus

Abstract

In plants, the carotenoid biosynthesis pathway (CBP) is essential for the production of photosynthetic and protective pigments, plant hormones, and visual/olfactory attractants for animal pollinators and seed dispersers. The regulation of carotenoid biosynthesis at the transcriptional level is vitally important for all of these functions and has been the subject of intensive research. Many putative transcriptional regulators, both direct and indirect, have been identified through conventional mutant analysis, transcriptome profiling, yeast one-hybrid screening, and candidate gene approaches. Despite this progress, our understanding of the transcriptional regulation of carotenoid biosynthesis remains fragmented and incomplete. Frequently, a stimulus or regulator is known, but the mechanism by which it affects transcription has not been elucidated. In other cases, mechanisms have been proposed (such as direct binding of a CBP gene promoter by a transcription factor), but function was tested only in vitro or in heterologous systems, making it unclear whether these proteins actually play a role in carotenoid regulation in their endogenous environments. Even in cases where the mechanism is relatively well understood, regulators are often studied in isolation, either in a single plant species or outside the context of other known regulators. This presents a conundrum: why so many candidate regulators but so little consensus? Here we summarize current knowledge on transcriptional regulation of the CBP, lay out the challenges contributing to this conundrum, identify remaining knowledge gaps, and suggest future research directions to address these challenges and knowledge gaps.

Stone Fruit as Biofactories of Phytochemicals With Potential Roles in Human Nutrition and Health

“…Regulation of carotenogenesis has been exhaustively investigated in tomato fruit and Arabidopsis, and it has been also comprehensively reviewed ( Llorente et al., 2017 ; Stanley and Yuan, 2019 ). Transcription factors such as phytochrome interacting factors (PIFs), ethylene response factors (ERFs), MADS ripening inhibitor factor (RIN) are some of the many TFs that modulate carotenoids synthesis.…”

“…light) and developmental cues control the carotenoid biosynthetic genes ( Llorente et al., 2016 ; Sun et al., 2018 ). The control of carotenoid accumulation is also exerted at posttranscriptional and posttranslational levels ( Stanley and Yuan, 2019 ). Biosynthesis, degradation, and storage mediate carotenoids homeostasis as well ( Li and Yuan, 2013 ).…”

Carotenoid biofortification in crop plants: citius, altius, fortius

“…Plant carotenoid biosynthesis is regulated at different levels, including transcriptional, post-translational and end product mediated feedback regulation [5,89,164]. In general, factors regulating transcript levels differ between green and non-photosynthetic tissues [165]. In [168].NAC1, a further NAC family member, showed the opposite effect [169,170].…”

Transcriptome Profiling of Ornithogalum dubium Leaves and Flowers to Identify Key Carotenoid Genes for CRISPR Gene Editing

“…Diverse gene expression patterns were observed at the unopened buds, young flowers and mature flowers of O. dubium. Transcription levels of carotenoid biosynthesis genes have been shown to be tightly associated with the carotenoid content and composition in many plant tissues; however, there are additional factors that regulate carotenoid accumulation [32]. Interestingly, PSY/comp149747_c3, LCYE/comp135178_c0, BCH/comp140581_c0, BCH/comp146354_c0 and ECH/comp143684_c1 transcription levels decreased during flower development.…”