Broomrape infestation in carrot (Daucus carota): Changes in carotenoid gene expression and carotenoid accumulation in the parasitic weed Phelipanche aegyptiaca and its host

Sewar Emran,Mosaab Yahyaa,Bhagwat Nawade,Dorothea Tholl,Jackline Abu Nassar,Mwafaq Ibdah,Hanan Eizenberg

doi:10.1038/s41598-019-57298-7

Sewar Emran, Mosaab Yahyaa + Show 5 more

Open Access

https://doi.org/10.1038/s41598-019-57298-7

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Abstract

Carotenogenesis has been intensively studied in carrot roots, and transcriptional regulation is thought to be the major factor in carotenoid accumulation in these organs. However, little is known about the transcriptional regulation of carotenoid biosynthetic genes concerning carotenoid accumulation during infestation by the obligate parasite Phelipanche aegyptiaca. HPLC analysis revealed a decrease in carotenoid levels of the different carrot cultivars when parasitized by P. aegyptiaca. Besides, we isolated and analyzed P. aegyptiaca tubercles parasitizing the various carrot root cultivars and show that they accumulate different carotenoids compared to those in non-infested carrot roots. Expression analysis of PHYTOENE SYNTHASE (PSY1) and CAROTENOID ISOMERASE (CRTISO) as well as the strigolactone apocarotenoid biosynthetic genes DWARF27 (D27), CAROTENOID CLEAVAGE DIOXYGENASE 7 (CCD7) and CCD8 revealed that their transcript levels showed significant variation in P. aegyptiaca infested carrot roots. After parasite infestation, the expression of these genes was strongly reduced, as were the carotenoid levels and this was more pronounced in the uncommon non-orange varieties. We also analyzed the parasite genes encoding D27, CCD7 and CCD8 and show that they are expressed in tubercles. This raises important questions of whether the parasite produces its carotenoids and apocarotenoids including strigolactones and whether the latter might have a role in tubercle development.

Highlights

The parasitic weeds of the genera Orobanche, Phelipanche, and Striga (Orobanchaceae) are the most important agricultural weeds in many crops, in carrot, tomato, sunflower, tobacco, and faba bean, causing significant crop losses in many parts of the world[1]
We show here that the concentration of carotenoids and the expression ofcarotenoid biosynthetic genes from different carrot cultivars were dramatically reduced in the Phelipanche-infested carrot root
The impact of P. aegyptiaca on the development of carrots cultivars, observed after 12 weeks of parasitism and results showed the drastic effect on all carrot cultivars (Fig. 2)

Summary

Introduction

The parasitic weeds of the genera Orobanche, Phelipanche, and Striga (Orobanchaceae) are the most important agricultural weeds in many crops, in carrot, tomato, sunflower, tobacco, and faba bean, causing significant crop losses in many parts of the world[1]. Hacham et al.[34] propose that P. aegyptiaca has its own metabolic mechanisms that enable the parasite to accumulate different metabolites derived from the host and/or modify/synthesize metabolites according to its own needs, which differ from those of its host This information encouraged us to analyze the transcript accumulation of the parasite P. aegyptiaca PaD27, PaCCD7, and PaCCD8 as well as carotenoid accumulations in the tubercle after carrot infestation. The concentration and composition of carotenoids and the expression of various genes of carotenoid metabolism were investigated in the roots of five different carrot cultivars infested or non-infested by P. aegyptiaca and in the tubercles of the parasitic plant. We show here that the concentration of carotenoids and the expression of (apo)carotenoid biosynthetic genes from different carrot cultivars were dramatically reduced in the Phelipanche-infested carrot root Alterations in these parameters concern host roots and the tubercles of the parasite

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