Showing papers on "Neoxanthin published in 2018"

Abscisic acid biosynthesis under water stress: anomalous behavior of the 9-cis-epoxycarotenoid dioxygenase1 (NCED1) gene in rice

Abstract: The gene NCED1 encodes 9-cis-epoxycarotenoid dioxygenase, which catalyzes oxidative cleavage of 9-cis-epoxycarotenoids neoxanthin and violaxanthin to xanthoxin, a key step in the biosynthesis of abscisic acid (ABA) in higher plants. In the present study, the complete NCED1 of 1 917 bp was cloned and characterized from rice (Oryza sativa L. cv. N22) as no earlier reports were available for its characterization from the indica cultivar. The NCED1 had no intron and encoded a protein of 639 amino acids with a predicted molecular mass of 68.62 kD and pI of 6.07. The aliphatic index and grand average of hydropathicity were found to be 77.04 and -0.148, respectively. Multiple alignment analysis revealed that the sequence shared a high identity with the Oryza sativa japonica group (100 %) followed by Triticum aestivum (90 %), Hordeum vulgare (90 %), and Zea mays (89 %). The enzyme had a RPE65 domain of 476 amino acid residues. The RPE65 domain requires Fe(II) as a cofactor coordinated with 4 histidine residues and 3 glutamic acid residues. The phylogenic tree shows that NCED1 of japonica rice and NCED1 of indica rice were in the same group. They might have been evolved from a common ancestor. Analysis with a PSORT III tool shows that NCED is a chloroplastic protein. The real-time quantitative PCR and RNA-sequencing studies show that the expression of NCED1 was progressively reduced with increasing water stress, and a negative correlation between expression of OsNCED1 and severity of stress was established. Further, NCED1 expression negatively correlated with ABA accumulation under water stress whereas in some other species, its expression increased along with ABA accumulation. This might be due to feedback inhibition of the ABA biosynthesis in rice.

Plant Photosynthetic Pigments: Methods and Tricks for Correct Quantification and Identification

Abstract: Chloroplast of green photosynthetic tissues in the Viridiplantae (monophyletic group that includes green algae and terrestrial plants) is characterised by a relatively conserved composition of pigments (Esteban et al. 2015). Leaves of virtually all plant species invariably contain chlorophyll (Chl) a and Chl b, and six carotenoids. Five of them are xanthophylls (carotenoids that contain oxygen): neoxanthin (Neo), lutein (Lut), violaxanthin (Vio), antheraxanthin (Ant) and zeaxanthin (Zea). The remaining carotenoid is a carotene (no oxygen in the molecule): β-carotene (β-Car). Additionally, certain taxa contain a second carotene: α-Car, which partially substitutes β-Car in some species under low light environment (Young and Britton 1989; Esteban and Garcia-Plazaola 2016). Some species phylogenetically unrelated also include lutein epoxide (Lx), a xanthophyll likewise related to shade acclimation (Matsubara et al. 2005; Esteban et al. 2009b). Regarding pigment concentration, in agreement with the relatively conserved composition of pigments across green photosynthetic organisms, and because the maximum Chl concentration per leaf is limited by specific and physiological constrains (Niinemets 2007), photosynthetic pigments are restricted within specific ranges of concentrations. Highly reliable ranges of pigment content for non-stressed plants that were obtained from two data-bases comprising more than 800 species can be found in (Esteban et al. 2015; Fernandez-Marin et al. 2017) (summarized as reference in Table 3.1).