Isolation and functional characterisation of banana phytoene synthase genes as potential cisgenes
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Carotenoids occur in all photosynthetic organisms where they protect photosystems from auto-oxidation, participate in photosynthetic energy transfer and are secondary metabolites. Of the more than 600 known plant carotenoids, few can be converted into vitamin A by humans and so these pro-vitamin A carotenoids (pVAC) are important in human nutrition. Phytoene synthase (PSY) is a key enzyme in the biosynthetic pathway of pVACs and plays a central role in regulating pVAC accumulation in the edible portion of crop plants. Banana is a major commercial crop and serves as a staple crop for more than 30 million people. There is natural variation in fruit pVAC content across different banana cultivars, but this is not well understood. Therefore, we isolated PSY genes from banana cultivars with relatively high (cv. Asupina) and low (cv. Cavendish) pVAC content. We provide evidence that PSY in banana is encoded by two paralogs (PSY1 and PSY2), each with a similar gene structure to homologous genes in other monocots. Further, we demonstrate that PSY2 is more highly expressed in fruit pulp compared to leaf. Functional analysis of PSY1 and PSY2 in rice callus and E. coli demonstrates that both genes encode functional enzymes, and that Asupina PSYs have approximately twice the enzymatic activity of the corresponding Cavendish PSYs. These results suggest that differences in PSY enzyme activity contribute significantly to the differences in Asupina and Cavendish fruit pVAC content. Importantly, Asupina PSY genes could potentially be used to generate new cisgenic or intragenic banana cultivars with enhanced pVAC content.
KeywordsBiofortification Carotene Cisgenic Intragenic Isoprenoid Metabolic engineering
Pro-vitamin A carotenoid
Vitamin A deficiency
The authors are grateful to: Doug Becker at QUT for coordinating the supply of plant material from Queensland Department of Employment, Economic Development and Innovation (DEEDI); Jeff Daniells at DEEDI (South Johnstone) for supplying Asupina green fruit tissue; Jennifer Kleidon at QUT for supplying Cavendish and Ladyfinger leaf tissue, maintenance of Asupina, Lakatan and Wain banana plants at QUT, and for training in rice tissue culture and transformation techniques; Sharon Hamill at DEEDI (Nambour) for supplying Asupina, Lakatan and Wain banana plants; Russell Reinke (Yanco Agricultural Institute) for supplying Nipponbare rice seeds; Queensland University of Technology International Doctorate Scholarship program for postgraduate scholarship support and funding. The research was funded by a grant from the Bill and Melinda Gates Foundation Grand Challenges in Global Health Initiative. The authors declare that they have no conflict of interest.
- Chu CC, Wang CS, Sun CS, Hsu C, Yin KC, Chu CY, Bi FY (1975) Establishment of an efficient medium for anther culture of rice through comparative experiments on the nitrogen sources. Sci Sinica 18:659–668Google Scholar
- Daniells J, Jenny C, Karamura D, Tomekpe K (2001) Diversity in the genus Musa. Musalogue: a catalogue of Musa germplasm. International Network for the Improvement of Banana and Plantain, MontpellierGoogle Scholar
- Howitt CA, Cavanagh CR, Bowerman AF, Cazzonelli C, Rampling L, Mimica JL, Pogson BJ (2009) Alternative splicing, activation of cryptic exons and amino acid substitutions in carotenoid biosynthetic genes are associated with lutein accumulation in wheat endosperm. Funct Integr Genomics 9:363–376PubMedCrossRefGoogle Scholar
- IITA (2009) Banana and plantain systems. http://www.iita.org/c/document_library/get_file?p_l_id=25410&folderId=27021&name=DLFE-172.pdf
- Larkin MA, Blackshields G, Brown NP, Chenna R, McGettigan PA, McWilliam H, Valentin F, Wallace IM, Wilm A, Lopez R, Thompson JD, Gibson TJ, Higgins DG (2007) Clustal W and Clustal X version 2.0. Bioinformatics (Oxford, England) 23:2947–2948Google Scholar
- Marchler-Bauer A, Lu S, Anderson JB, Chitsaz F, Derbyshire MK, DeWeese-Scott C, Fong JH, Geer LY, Geer RC, Gonzales NR, Gwadz M, Hurwitz DI, Jackson JD, Ke Z, Lanczycki CJ, Lu F, Marchler GH, Mullokandov M, Omelchenko MV, Robertson CL, Song JS, Thanki N, Yamashita RA, Zhang D, Zhang N, Zheng C, Bryant SH (2011) CDD: a conserved domain database for the functional annotation of proteins. Nucleic Acids Res 39:D225–D229PubMedCrossRefGoogle Scholar
- Pillay M, Tenkouano A, Ude G, Ortiz R (2004) Molecular characterization of genomes in Musa and its applications. In: Jain SM, Swennen R (eds) Banana improvement: cellular, molecular biology, and induced mutations, Chapter 23. Science Publishers, Enfield, NH, USAGoogle Scholar
- Schledz M, Al Babili S, Von Lintig J, Haubruck H, Rabbani S, Kleinig H, Beyer P (1996) Phytoene synthase from Narcissus pseudonarcissus: functional expression, galactolipid requirement, topological distribution in chromoplasts and induction during flowering. Plant J 10:781–792PubMedCrossRefGoogle Scholar
- Sharrock S, Frison E (1998) Musa production around the world—trends, varieties and regional importance. Netw Banana Plantain Ann Rep 1998:41–46Google Scholar