| Phytochemicals | Vegetables | Role in human health |
| Lycopene | Tomato, Watermelon and Carrot | Protect against cancer, fight infection |
| Betacyanins | Beet root | High anti-oxidative, free radical scavenging activities |
| Beta-carotene | Carrot, Cantaloupe, Pumpkin, Sweet Potato and cauliflower | Antioxidant |
| Anthocyanins | Brinjal, carrot, amaranth, dolichos bean, cabbage and broccoli | Cardiovascular dysfunction, protective effect on pancreatic cells |
| Lutein | Yellow corn, carrot and sweet pepper | Good for eyes |
| Chlorophyll | Broccoli, Kale, Spinach, Cabbage and Asparagus | Act as a chemopreventive compound |
| Chlorogenic acid, nasunin | brinjal | Anti-carcinogenic, anti-obesity, and anti-diabetic properties |
| Quercetin | Onion | Heart disease, diabetes, peptic ulcer, inflammation, asthma, gout, viral infections |
| Indole-3-carvinol, gluconapin, Sulfaforaphane | Cauliflower, broccoli | Protect against cancer, heart disease and stroke |
| Allyl propyl disulfide, d-allyl disulfide | Onion, garlic | Protect against certain cancers and heart disease, boost the immune system |
| Flavonoids (isoflavones) | Bens | Protect against cancer, lower cholesterol |
| Momordicin and Charantin | Bittergourd | Diabetes, Blood purifier, Hypertension, Dysentery, Anathematic |
Biotechnological approach for improving bioactive compounds
Marker assisted breeding using genetic map and QTL analysis
Tomato: QTL associated with carotenoids using introgression populations of Solanum pennellii, S. peruvianum and S. hirsutum have been described by Bernacchi et al. (1998). The dominant gene Anthocyanin fruit (Aft), which induces limited pigmentation upon stimulation by high light intensity, was introgressed into domesticated tomato plants by an interspecific cross with S. chilense (Jones, 2003; Mes, 2008). Similarly, the gene Aubergine (Abg), which was introgressed from Solanum lycopersicoides, can induce a strong and variegated pigmentation in the peel of tomatoes.
Brassica vegetables: The 'or' mutation in Chinese cabbage is a recessive, single-locus mutation give carotenoid pigments in head leaves of the plant (Zhang et al., 2008). Fenglan (2008) found SCAR markers linked to “or” gene inducing beta-carotene accumulation in Chinese cabbage. Ripley and Roslinsky (2005) identified an ISSR Marker for 2-propenyl glucosinolate content in Brassica.
Sweet potato: Cervantes-Flores et al. (2010) have also recently reported QTLs in sweet potato for high dry matter, starch content and Beta-carotene which leads to opening up the possibility of genetic manipulation and further enhancement of this root crop.
Carrot: Seven monogenic traits have been mapped for carrot: yel, cola, Rs, Mj-1, Y, Y2, and P1. QTL have been mapped for carrot total carotenoids and five component carotenoids; phytoene, Alpha-carotene, Beta-carotene, zeta-carotene, and lycopene (Santos and Simon, 2002) and the majority of the structural genes of the carotenoid pathway is now placed into this map (Just et al., 2007)
Genetic engineering approach
For beta-carotene
Tomato: To enhance the carotenoid content and profile of tomato fruit, Romer et al. (2000) produced transgenic lines containing a bacterial carotenoid gene (crtI) encoding the enzyme phytoene desaturase, which converts phytoene into lycopene. Diretto et al. (2006) have silenced the first step in the beta-epsilon branch of carotenoid biosynthesis, lycopene epsilon cyclase (LCY-e) in potato, a tuber crop that contains low levels of carotenoids. This antisense tuber-specific silencing of the gene results in significant increases in carotenoid levels, with up to 14-fold more Beta-carotene.
Potato: Direttoet al. (2007) introduced three genes, encoding phytoene synthase (CrtB), phytoenedesaturase (CrtI) and lycopene beta-cyclase (CrtY) from Erwinia in potato to produce beta carotene. Gerjets and Sandmann (2006) developed genetically engineered potato for the production of commercially important keto carotenoids including astaxanthin (3, 3'-dihydroxy 4, 4'-diketo-Beta-carotene).
Sweet potato: Kim et al. (2012) developed transgenic sweet potato through the inhibition of hydroxylation of b-carotene, the effects of silencing CHY-b in the carotenoid biosynthetic pathway. In transgenic line #7, the total carotenoid content reached a maximum of 117 lg/g dry weight, of which b-carotene measured 34.43 lg/g dry weights.
Cauliflower: Lu et al. (2006) developed transgenic cauliflower with high levels of Beta-carotene accumulation. Transformation of the 'or' gene into wild type cauliflower converts the white colour of curd tissue into distinct orange colour with increased level of Beta-carotene.
For anthocyanin
Tomato: In tomato, overexpression of Anthocyanin 1 (Ant1), a transcription factor regulating anthocyanin production has led to the accumulation of anthocyanins in fruit skin and a layer immediately below it (Mathews et al., 2003). Maligeppagol et al. (2013) developed transgenic tomato accumulating high amounts (70"100 fold) of anthocyanin in the fruits by fruit specific expression of two transcription factors, Delila and Rosea1 isolated from Antirrhinum majus. The transgenic tomato plants were identical to the control plants, except for the accumulation of high levels of anthocyanin pigments throughout the fruit during maturity, thus giving the fruit a purplish colour. Stushnoff et al. (2010) in potato identified 27 genes that are differentially expressed in purple and white tuber tissues.
For folates
Tomato: Garza et al. (2004, 2007) developed transgenic tomatoes by engineering fruit- specific overexpression of GTP cyclohydrolase I that catalyzes the first step of pteridine synthesis, and amino-deoxy-chorismate synthase that catalyzes the first step of PABA synthesis. Vine-ripened fruits contained on average 25-fold more folate than controls by combining PABA and pteridine overproduction traits through crossbreeding of transgenic tomato plants.
For glucosinolate
Cole crops: Chromosome segments from a wild ancestor, Brassica villosa, have been introgressed to enhance glucosinolate levels such as indole-3-carbinol or sulphoraphane. Hence, high glucosinolate broccoli might be suitable for increasing the amount of sulphoraphane in the diet (Sarikamis et al., 2006). Three high-glucoraphanin F1 broccoli hybrids were developed through genome introgression from the wild species Brassica villosa and contained a B. villosa Myb28 allele. Two high-glucoraphanin hybrids have been commercialized as Beneforte broccoli (Traka et al., 2013).
For allicin
Onion: Three sets of transgenic onion plants containing antisense alliinase gene constructs (a CaMV 35S-driven antisense root alliinase gene, a CaMV 35S-driven antisense bulb alliinase, and a bulb alliinase promoter-driven antisense bulb alliinase) have been produced (Eady et al., 2003).
References
1. Chakraborty, S., Chakraborty, N., Agrawal, A., Ghosh, S., Narula, K., Shekhar, S., Naik, P.S., Pande, P. C., Chakrborti, S.K. and Dattaa, A. (2010).Next-generation protein-rich potato expressing the seed protein gene AmA1 is a result of proteome rebalancing in transgenic tuber. Proc Natl Acad Sci U S A. 107: 17533-17538.
2. Feng, H., Y. Li, Z. Liu and J. Liu (2012). Mapping of or, a gene conferring orange color on the inner leaf of the Chinese cabbage (Brassica rapa L. ssp. pekinensis). Mol. Breed. 29: 235-244.
3. Jones, C.M.,Mes, P. and Myers, J.R. (2003).Characterization and inheritance of theAnthocyanin fruit (Aft) tomato.J. Hered. 94: 449"456.
4. Liu, Y.S., Gur, A., Ronen, A., Causse, M., Damidaux, R., Buret, M., Hirschberg, J. and Zamir, D. (2003). There is more to tomato fruit colour than candidate carotenoid genes .Plant Biotech. J.1 (3): 131-240.
5. Lu, S., Eck, J.V., Zhou, X., Lopez, A.B., Halloran. M., Cosman,K. M., Conlin, B. J., Paolillo,D. J., Garvinm, D. F., Vrebalov, J., Kochian, L. V., Kupper, H., Earle, E. D. Cao, J. and Li, L. (2006). The CauliflowerOr Gene Encodes a DnaJ Cysteine-Rich Domain-Containing Protein That Mediates High Levels of Beta-Carotene Accumulation. The Plant Cell.18: 3594-3605.
6. Mes P.J., Boches, P., Myers, J.R., Durst, R.(2008) Characterization of tomatoes expressinganthocyanin in the fruit.J. Am. Soc. Hortic. Sci.133: 262"269.
7. Sapir,M., Shamir,M.O., Ovadia,R., Reuveni, M.,Evenor,D.,Tadmor,Y., Nahon,S., Shlomo, H., Chen, L., Meir,A. andLevin,I. (2008). Molecular Aspects of Anthocyanin fruit Tomato in Relation to high pigment-1, J. Hered. 99 (3):292-303.
8. Traka, M.H., Saha, S., Huseby, S. and Mithen, R.F. (2013). Genetic regulation of glucoraphanin accumulation in Beneforte broccoli.New Phytol.198(4): 1085"1095.
About Author / Additional Info:
I am working on improvement of vegetable through conventional and biotechnological approach