Development of a direct transformation method by GFP screening and in vitro whole plant regeneration of Capsicum frutescens L

Enhancing genetic modification in recalcitrant plants: An investigation in chili (Capsicum annuum) through the optimized tape sandwich protoplast isolation and polyethylene glycol-mediated transfection

Chili presents challenges for Agrobacterium-mediated transfection due to its highly recalcitrant nature. One way to overcome this challenge is by using PEG-mediated transfection of protoplasts, which enhances the likelihood of successfully introducing transgenes into the cells. The tape sandwich method for isolating chili leaf protoplasts was optimized by adjusting enzyme concentrations and incubation duration, resulting in a high yield of 1.3×106 cells ml-1 per 0.1 g of leaves. The efficiency of transfecting GFP-encoding plasmids and Cas9 protein using PEG molecules of different sizes was also examined. The highest plasmid transfection efficiency was achieved with 5 µg of plasmid in 50 µl-1, with an average efficiency of 48.71%. For Cas9 protein transfection, the most effective treatment involved using 1000 µg of protein in 100 µl-1, mediated by 40% PEG 4000, resulting in an average efficiency of 2.94% due to protein aggregation. Nevertheless, this optimized protocol reduces the time required for chili protoplast isolation and enhances plasmid transfection efficiency by nearly 50%.

Developing an Optimized Protocol for Regeneration and Transformation in Pepper

Capsicum annuum L. is extensively cultivated in subtropical and temperate regions globally, respectively, when grown in a medium with 8 holding significant economic importance. Despite the availability of genome sequences and editing tools, gene editing in peppers is limited by the lack of a stable regeneration and transformation method. This study assessed regeneration and transformation protocols in seven chili pepper varieties, including CM334, Zunla-1, Zhongjiao6 (ZJ6), 0818, 0819, 297, and 348, in order to enhance genetic improvement efforts. Several explants, media compositions, and hormonal combinations were systematically evaluated to optimize the in vitro regeneration process across different chili pepper varieties. The optimal concentrations for shoot formation, shoot elongation, and rooting in regeneration experiments were determined as 5 mg/L of 6-Benzylaminopurine (BAP) with 5 mg/L of silver nitrate (AgNO3), 0.5 mg/L of Gibberellic acid (GA3), and 1 mg/L of Indole-3-butyric acid (IBA), respectively. The highest regeneration rate of 41% was observed from CM334 cotyledon explants. Transformation optimization established 300 mg/L of cefotaxime for bacterial control, with a 72-h co-cultivation period at OD600 = 0.1. This study optimizes the protocols for chili pepper regeneration and transformation, thereby contributing to genetic improvement efforts.

Molecular basis of heterosis and related breeding strategies reveal its importance in vegetable breeding

Heterosis has historically been exploited in plants; however, its underlying genetic mechanisms and molecular basis remain elusive. In recent years, due to advances in molecular biotechnology at the genome, transcriptome, proteome, and epigenome levels, the study of heterosis in vegetables has made significant progress. Here, we present an extensive literature review on the genetic and epigenetic regulation of heterosis in vegetables. We summarize six hypotheses to explain the mechanism by which genes regulate heterosis, improve upon a possible model of heterosis that is triggered by epigenetics, and analyze previous studies on quantitative trait locus effects and gene actions related to heterosis based on analyses of differential gene expression in vegetables. We also discuss the contributions of yield-related traits, including flower, fruit, and plant architecture traits, during heterosis development in vegetables (e.g., cabbage, cucumber, and tomato). More importantly, we propose a comprehensive breeding strategy based on heterosis studies in vegetables and crop plants. The description of the strategy details how to obtain F1 hybrids that exhibit heterosis based on heterosis prediction, how to obtain elite lines based on molecular biotechnology, and how to maintain heterosis by diploid seed breeding and the selection of hybrid simulation lines that are suitable for heterosis research and utilization in vegetables. Finally, we briefly provide suggestions and perspectives on the role of heterosis in the future of vegetable breeding.