Anchorene is an endogenous diapocarotenoid required for anchor root formation in Arabidopsis

Abstract

Arabidopsis root development is predicted to be regulated by yet unidentified carotenoidderived metabolite(s). In this work, we screened known and putative carotenoid cleavage products and identified anchorene, a predicted carotenoid-derived dialdehyde (diapocarotenoid) that triggers anchor root development. Anchor roots are the least characterized type of root in Arabidopsis. They form at the root-shoot junction, particularly upon damage to the root apical meristem. Using Arabidopsis reporter lines, mutants and chemical inhibitors, we show that anchor roots originate from pericycle cells and that the development of this root type is auxindependent and requires carotenoid biosynthesis. Transcriptome analysis and treatment of auxinreporter lines indicate that anchorene triggers anchor root development by modulating auxin homeostasis. Exogenous application of anchorene restored anchor root development in carotenoid-deficient plants, indicating that this compound is the carotenoid-derived signal required for anchor root development. Chemical modifications of anchorene led to a loss of anchor root promoting activity, suggesting that this compound is highly specific. Furthermore, we demonstrate by LC-MS analysis that anchorene is a natural, endogenous Arabidopsis metabolite. Taken together, our work reveals a new member of the family of carotenoid-derived regulatory metabolites and hormones. SignificanceUnknown carotenoid-derived compounds are predicted to regulate different aspects of plant development. Here, we characterize the development of anchor roots, the least characterized root type in Arabidopsis, and show that this process depends on auxin and requires a carotenoid-derived metabolite. We identified a presumed carotenoid-derivative, anchorene, as the likely, specific signal involved in anchor root formation. We further show that anchorene is a natural metabolite that occurs in Arabidopsis. Based on the analysis of auxin reporter lines and transcriptome data, we provide evidence that anchorene triggers the growth of anchor roots by modulating auxin homeostasis. Taken together, our work identifies a novel carotenoid-derived growth regulator with a specific developmental function.

Apocarotenoids Involved in Plant Development and Stress Response

“…Recently, Jia et al established a screening system to identify known and predicted diapocarotenoids involved in plant development, by assaying alterations in Arabidopsis roots. This approach led to the discovery of the presumed diapocarotenoid anchorene as a novel carotenoid-derived bioactive that promotes the development of anchor roots (ANRs) (Jia et al, 2019a), a less investigated type of Arabidopsis roots, which develop from the collet region situated at the root hypocotyl junction (Lucas et al, 2011). Although it is still unclear how it is formed, anchorene (C 10 ) is a natural metabolite, as confirmed by LC-MS analysis (Jia et al, 2019a; Mi et al, 2019a), and its structure indicates that it can be produced by cleaving the (C11–C12) and (C11′–C12′) double bound from all carotenoids downstream of ζ-carotene in the carotenoid biosynthesis pathway ( Figure 5B ).…”

“…In Arabidopsis , application of anchorene induces ANR formation. The regulation of ANR by anchorene is highly specific to its chemical structure, as application of a structural isomer did not show an effect on ANR development, and altering anchorene functional group(s) to alcohol, acid, or acid-ethyl ester resulted in a loss of activity (Jia et al, 2019a). The usage of auxin reporter lines and an auxin transport inhibitor, together with transcriptome analysis, showed that anchorene’s effect on ANR development is caused by modulating auxin homeostasis.…”

“…Indicating their role in increasing nitrogen uptake, Jia et al showed that ANR formation is triggered by nitrogen deficiency. Interestingly, lack of nitrogen led also to an increase in anchorene content, pointing to a possible function in regulating plant’s response to this adverse growth condition (Jia et al, 2019a).…”

A Highly Sensitive SPE Derivatization–UHPLC–MS Approach for Quantitative Profiling of Carotenoid-Derived Dialdehydes from Vegetables

“…For instance, it was very recently reported that anchorene, a C 10 DIAL, is a signaling molecule that regulates root development in Arabidopsis and rice. 13 In addition, studies on rosafluene, a C 14 DIAL, and its structural isomer demonstrated that they inhibit the activity of nuclear factor kappa B in bone and cancer cells and reduce the growth of breast and prostate cancer cells. 21 , 22 These results indicate the importance of DIALs for nutrition and plant science.…”

A Method for Extraction and LC-MS-Based Identification of Carotenoid-Derived Dialdehydes in Plants

“…Thus, the class of carotenoid-derivatives includes hormones, such as abscisic acid and strigolactone, [18][19][20][21][22][23][24][25], retinoids, i.e. retinal, retinol (vitamin A), and retinoic acid [26][27][28], the fungal pheromone trisporic acid [29,30], the stress signaling molecule β-cyclocitral [31][32][33], the recently discovered growth regulators anchorene and zaxinone [34,35], pigments, such as crocin in saffron [36], citraurin in citrus fruits [37], and the fungal neurosporaxanthin [38,39], and volatiles, such as safranal [40,41], geranial [42] and β-ionone [43,44]. All of these bioactive metabolites (named apocarotenoids) are generated by oxidative cleavage of carotenoids, which is generally catalyzed by carotenoid cleavage dioxygenases (CCDs) or by nonenzymatic oxidation caused by reactive oxygen species (ROSs) [25,32,45,46].…”