title: Overexpression of Crocus carotenoid cleavage dioxygenase, CsCCD4b, in Arabidopsis imparts tolerance to dehydration, salt and oxidative stresses by modulating ROS machinery.
abstract: Apocarotenoids modulate vital physiological and developmental processes in plants. These molecules are formed by the cleavage of carotenoids, a reaction catalyzed by a family of enzymes called carotenoid cleavage dioxygenases (CCDs). Apocarotenoids like β-ionone and β-cyclocitral have been reported to act as stress signal molecules during high light stress in many plant species. In Crocus sativus, these two apocarotenoids are formed by enzymatic cleavage of β-carotene at 9, 10 and 7, 8 bonds by CsCCD4 enzymes. In the present study three isoforms of CsCCD4 were subjected to molecular modeling and docking analysis to determine their substrate specificity and all the three isoforms displayed high substrate specificity for β-carotene. Further, expression of these three CsCCD4 isoforms investigated in response to various stresses revealed that CsCCD4a and CsCCD4b exhibit enhanced expression in response to dehydration, salt and methylviologen, providing a clue towards their role in mediating plant defense response. This was confirmed by overexpressing CsCCD4b in Arabidopsis. The transgenic plants developed longer roots and possessed higher number of lateral roots. Further, overexpression of CsCCD4b imparted enhanced tolerance to salt, dehydration and oxidative stresses as was evidenced by higher survival rate, increased relative root length and biomass in transgenic plants as compared to wild type. Transgenic plants also displayed higher activity and expression of reactive oxygen species (ROS) metabolizing enzymes. This indicates that β-ionone and β-cyclocitral which are enzymatic products of CsCCD4b may act as stress signals and mediate reprogramming of stress responsive genes which ultimately leads to plant defense.
authors.affiliation: Plant Biotechnology Division, CSIR-Indian Institute of Integrative Medicine, Sanat Nagar, Srinagar, Jammu and Kashmir 190005, India; Academy of Scientific and Innovative Research, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi 180 001, India.
authors.forename: Shoib Ahmad
authors.initials: SA
authors.lastname: Baba
authors.affiliation: Inter-disciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi 110021, India.
authors.forename: Deepti
authors.initials: D
authors.lastname: Jain
authors.affiliation: Plant Biotechnology Division, CSIR-Indian Institute of Integrative Medicine, Sanat Nagar, Srinagar, Jammu and Kashmir 190005, India.
authors.forename: Nazia
authors.initials: N
authors.lastname: Abbas
authors.affiliation: Plant Biotechnology Division, CSIR-Indian Institute of Integrative Medicine, Sanat Nagar, Srinagar, Jammu and Kashmir 190005, India; Academy of Scientific and Innovative Research, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi 180 001, India. Electronic address: nashraf@iiim.ac.in.
authors.forename: Nasheeman
authors.initials: N
authors.lastname: Ashraf
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002338:Carotenoids / Q000378:metabolism*; D027622:Crocus / Q000201:enzymology* / Q000235:genetics; D003681:Dehydration; D049308:Dioxygenases / Q000235:genetics / Q000378:metabolism*; D004224:Diterpenes / Q000378:metabolism; D008961:Models, Structural; D062105:Molecular Docking Simulation; D045792:Norisoprenoids / Q000378:metabolism; D018384:Oxidative Stress; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012965:Sodium Chloride / Q000494:pharmacology; D019207:beta Carotene / Q000378:metabolism
chemical_list: D000447:Aldehydes; D004224:Diterpenes; D045792:Norisoprenoids; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D019207:beta Carotene; D002338:Carotenoids; D012965:Sodium Chloride; C516118:beta-cyclocitral; C008157:beta-ionone; D049308:Dioxygenases
keywords: Apocarotenoids; Carotenoid cleavage dioxygenase; Carotenoids; Crocus sativus; β-Cyclocitral; β-Ionone