Apocarotenoids Involved in Plant Development and Stress Response

Abstract

Carotenoids are isoprenoid pigments synthesized by all photosynthetic organisms and many heterotrophic microorganisms. They are equipped with a conjugated double-bond system that builds the basis for their role in harvesting light energy and in protecting the cell from photo-oxidation. In addition, the carotenoids polyene makes them susceptible to oxidative cleavage, yielding carbonyl products called apocarotenoids. This oxidation can be catalyzed by carotenoid cleavage dioxygenases or triggered nonenzymatically by reactive oxygen species. The group of plant apocarotenoids includes important phytohormones, such as abscisic acid and strigolactones, and signaling molecules, such as β-cyclocitral. Abscisic acid is a key regulator of plant's response to abiotic stress and is involved in different developmental processes, such as seed dormancy. Strigolactone is a main regulator of plant architecture and an important signaling molecule in the plant-rhizosphere communication. β-Cyclocitral, a volatile derived from β-carotene oxidation, mediates the response of cells to singlet oxygen stress. Besides these wellknown examples, recent research unraveled novel apocarotenoid growth regulators and suggests the presence of yet unidentified ones. In this review, we describe the biosynthesis and biological functions of established regulatory apocarotenoids and touch on the recently identified anchorene and zaxinone, with emphasis on their role in plant growth, development, and stress response.

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“…Carotenoids absorb light energy, participate in photosynthesis, protect plants against oxidative damage, and are precursors of visual pigment chromophores and volatile apocarotenoids that attract pollinators (Heath et al, 2013;Sun et al, 2018). Moreover, they are involved in plant responses to abiotic stresses and plant-microbe interactions (Felemban et al, 2019). Among carotenoids, blumenols also accumulated in the biostimulant-treated plants.…”

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“…A decrease in carotenoid intensity may suggest that photosynthetic processes are disrupted upon HLB infection and thus correlates with the blotchy mottle/chlorosis symptoms typical for HLB. Additionally, the carotenoids could be metabolized to apocarotenoids, or other volatile signaling molecules that could function as a stress adaptation 22 . Lignin and related secondary metabolites not only act as physical barriers to invading plant pathogens but can also play a key role in plant defense signaling 23 .…”

Microbial-based biostimulant enhances sweet pepper performance by metabolic reprogramming of phytohormone profile and secondary plant metabolism

“…Carotenoids absorb light energy, participate in photosynthesis, protect plants against oxidative damage, and are precursors of visual pigment chromophores and volatile apocarotenoids that attract pollinators (Heath, Cipollini, & Stireman, 2013;Sun, et al, 2018). Moreover, they are involved in plant responses to abiotic stresses and plant-microbe interactions (Felemban, Braguy, Zurbriggen, & Al-Babili, 2019). Blumenols comprise a class of apocarotenoids or cyclohexanone derivatives of carotenoid cleavage.…”