Chilli peppers — A review on tissue culture and transgenesis

Overexpression of the CaTIP1-1 pepper gene in tobacco enhances resistance to osmotic stresses

Both the gene expression and activity of water channel protein can control transmembrane water movement. We have reported the overexpression of CaTIP1-1, which caused a decrease in chilling tolerance in transgenic plants by increasing the size of the stomatal pore. CaTIP1-1 expression was strongly induced by salt and mannitol stresses in pepper (Capsicum annuum). However, its biochemical and physiological functions are still unknown in transgenic tobacco. In this study, transient expression of CaTIP1-1-GFP in tobacco suspension cells revealed that the protein was localized in the tonoplast. CaTIP1-1 overexpressed in radicle exhibited vigorous growth under high salt and mannitol treatments more than wild-type plants. The overexpression of CaTIP1-1 pepper gene in tobacco enhanced the antioxidant enzyme activities and increased transcription levels of reactive oxygen species-related gene expression under osmotic stresses. Moreover, the viability of transgenic tobacco cells was higher than the wild-type after exposure to stress. The pepper plants with silenced CaTIP1-1 in P70 decreased tolerance to salt and osmotic stresses using the detached leaf method. We concluded that the CaTIP1-1 gene plays an important role in response to osmotic stresses in tobacco.

Pharmacological importance of an ethnobotanical plant: Capsicum annuum L

Capsicum annuum L., a fruit plant from tropical and subtropical regions, contains a range of essential nutrients and bioactive compounds which are known to exhibit a range of bioactivities including free radical scavenging (antioxidant), antimicrobial, antiviral, anti-inflammatory and anticancer. This review aims to give a comprehensive overview of the literature published on pharmacological behaviours of C. annuum L.

Effects of Different Cooking Methods on the Antioxidant Properties of Red Pepper (Capsicum annuum L.)

We investigated the effect of various cooking methods (boiling, steaming, stir-frying, and roasting) and three cooking times (5, 10, and 15 min) on the antioxidant properties of red pepper. Raw and cooked peppers were measured for proximate composition, ascorbic acid (AsA) content, total carotenoid content (TCC), total polyphenol content (TP), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities. Results showed that the proximate composition, AsA content, TCC, TP, and antioxidant activities were significantly (p<0.05) affected by the cooking procedure; the loss rate varied among individual compounds. Boiling and steaming significantly reduced AsA content (24.3~66.5%), TP (13.9~ 54.9%), and antioxidant activity (21.7~60.5%) in red pepper, while stir-frying and roasting slightly reduced AsA content (2.7~25.9%), TP (1.8~4.9%), and antioxidant activity (4.9~17.9%). The highest loss was observed after boiling, followed by steaming, roasting, and stir-frying. Stir-frying and roasting better preserved AsA content, TCC, TP, and antioxidant activity. In conclusion, dry-heat cooking methods such as stir-frying and roasting may be preferred to retain the nutrient compositions and antioxidant properties of red pepper.

Functional validation of Capsicum frutescens aminotransferase gene involved in vanillylamine biosynthesis using Agrobacterium mediated genetic transformation studies in Nicotiana tabacum and Capsicum frutescens calli cultures

Capsaicinoid biosynthesis involves the participation of two substrates viz. vanillylamine and C(9)-C(11) fatty acid moieties. Vanillylamine which is a derivative of vanillin is synthesized through a transaminase reaction in the phenylpropanoid pathway of capsaicinoid synthesis. Here we report the functional validation of earlier reported putative aminotransferase gene for vanillylamine biosynthesis in heterologous system using Agrobacterium mediated genetic transformation studies in Nicotiana tabacum and Capsicum frutescens calli cultures. Molecular analysis tools comprising PCR and Southern blot analysis have shown the integration of the foreign gene in N. tabacum and C. frutescens calli cultures. The study shows the production of vanillylamine in transformed N. tabacum callus cultures and also the reduction of vanillylamine production when whole gene based antisense binary vector construct was used in transformation of C. frutescens callus cultures. Vanillylamine production, aminotransferase assay with Western blot analysis for crude proteins of transformants established the production of putative aminotransferase (pAMT) protein in alternate plant. The result is a clear evidence of involvement of the reported putative aminotransferase responsible for vanillylamine biosynthesis in capsaicinoid biosynthesis pathway, confirming the gene function through functional validation.

In vitro culture of lavenders (Lavandula spp.) and the production of secondary metabolites

Lavenders (Lavandula spp., Lamiaceae) are aromatic ornamental plants that are used widely in the food, perfume and pharmaceutical industries. The large-scale production of lavenders requires efficient in vitro propagation techniques to avoid the overexploitation of natural populations and to allow the application of biotechnology-based approaches for plant improvement and the production of valuable secondary metabolites. In this review we discuss micropropagation methods that have been developed in several lavender species, mainly based on meristem proliferation and organogenesis. Specific requirements during stages of micropropagation (establishment, shoot multiplication, root induction and acclimatization) and requisites for plant regeneration trough organogenesis, as an important step for the implementation of plant improvement programs, were revised. We also discuss different methods for the in vitro production of valuable secondary metabolites, focusing on the prospects for highly scalable cultures to meet the market demand for lavender-derived products.

The optimization of regeneration tissue culture system of three chilli peppers cultivars based on the uniform design and the mathematical model equation

Using uniform random design optimization and the mathematical model equation we optimized the regeneration tissue culture system of the chilli pepper. An efficient and detailed plant reproducible protocol in vitro has been established using different explants and induction media for three chilli pepper cultivars. The result displayed that the seedlings at the curved hypocotyl stage were the best choice to prepare for explants, the genotype of explants affected shoot buds induction frequency and number of shoot buds per explant, and the cotyledon explant was more responsive than hypocotyl explant. The optimal media for maximum shoot initiation and regeneration and the optimal elongation medium were obtained. For Capsicum annuum var. annuum (cv. Xinsu), Capsicum annuum var. annuum (cv. Neimengchifeng) and Capsicum frutescens (cv. Xingfu), the induction rates were 99.17%, 97.50 and 96.11%, respectively; the elongation rates of shoot buds were 86.67%, 85.19% and 82.96%, respectively. The MS medium with 0.57 μM IAA and 0.69 μM NAA is the best choice for root induction. The frequency of their root emergence was 95.00-98.33%. Regenerated chilli peppers were successfully acclimatized and cultivated with 100% survival. This work will help to improve multiplication process and the genotype of chilli pepper, and may have commercial impact.

In vitro plantlet regeneration from nodal segments and shoot tips of Capsicum chinense Jacq. cv. Naga King Chili

An in vitro regeneration protocol was developed for Capsicum chinense Jacq. cv. Naga King Chili, a very pungent chili cultivar and an important horticultural crop of Nagaland (Northeast India). Maximum number of shoot (13 ± 0.70) was induced with bud-forming capacity (BFC) index of 10.8, by culturing nodal segments in Murashige and Skoog (MS) medium supplemented with 18.16 μM Thidiazuron (TDZ) followed by 35.52 μM 6-benzylaminopurine (BAP). Using shoot tips as explants, multiple shoot (10 ± 0.37) (BFC 8.3) was also induced in MS medium fortified with either 18.16 μM TDZ or 35.52 μM BAP. Elongated shoots were best rooted in MS medium containing 5.70 μM indole-3-acetic acid (IAA). Rooted plantlets thus developed were hardened in 2–3 weeks time in plastic cups containing potting mixture of a 1:1 mix of soil and cow dung manure and then subsequently transferred to earthen pots. The regenerated plants did not show any variation in the morphology and growth as compared to the parent plant.

Efficient sweet pepper transformation mediated by the BABY BOOM transcription factor

Pepper (Capsicum L.) is a nutritionally and economically important crop that is cultivated throughout the world as a vegetable, condiment, and food additive. Genetic transformation using Agrobacterium tumefaciens (agrobacterium) is a powerful biotechnology tool that could be used in pepper to develop community-based functional genomics resources and to introduce important agronomic traits. However, pepper is considered to be highly recalcitrant for agrobacterium-mediated transformation, and current transformation protocols are either inefficient, cumbersome or highly genotype dependent. The main bottleneck in pepper transformation is the inability to generate cells that are competent for both regeneration and transformation. Here, we report that ectopic expression of the Brassica napus BABY BOOM AP2/ERF transcription factor overcomes this bottleneck and can be used to efficiently regenerate transgenic plants from otherwise recalcitrant sweet pepper (C. annuum) varieties. Transient activation of BABY BOOM in the progeny plants induced prolific cell regeneration and was used to produce a large number of somatic embryos that could be converted readily to seedlings. The data highlight the utility of combining biotechnology and classical plant tissue culture approaches to develop an efficient transformation and regeneration system for a highly recalcitrant vegetable crop.

Androgenesis in recalcitrant solanaceous crops

Tomato, eggplant, and pepper are three solanaceous crops of outstanding importance worldwide. For hybrid seed production in these species, a fast and cheap method to obtain pure (homozygous) lines is a priority. Traditionally, pure lines are produced by classical inbreeding and selection techniques, which are time consuming (several years) and costly. Alternatively, it has become possible to accelerate the production of homozygous lines through a biotechnological approach: the induction of androgenesis to generate doubled haploid (homozygous) plants. This biotechnological in vitro tool reduces the process to only one generation, which implies important time and costs savings. These facts make androgenic doubled haploids the choice in a number of important crops where the methodology is well set up. Unfortunately, recalcitrant solanaceous crops such as tomato, eggplant, and pepper are still far from an efficient and reliable technology to be applied on a routine basis to different genotypes in breeding programs. In eggplant and pepper, only anther cultures are known to work relatively well. Unfortunately, a more efficient and promising technique, the culture of isolated microspores, is not sufficiently developed yet. In tomato, none of these methods is available nowadays. However, recent advances in the knowledge of embryo development are filling the gaps and opening new ways to achieve the final goal of an efficient protocol in these three recalcitrant species. In this review, we outline the state of the art on androgenic induction in tomato, eggplant, and pepper, and postulate new experimental ways in order to overcome current limitations.