Efficient sweet pepper transformation mediated by the BABY BOOM transcription factor

Abstract

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.Electronic supplementary materialThe online version of this article (doi:10.1007/s00299-011-1018-x) contains supplementary material, which is available to authorized users.

A transcriptional view on somatic embryogenesis

“…BBM overexpression also induces other types of regeneration, including callus and adventitious shoot and root formation. This property has been exploited to improve transformation in crop and model plants (Deng, Luo, Li, & Yang, 2009; Florez, Erwin, Maximova, Guiltinan, & Curtis, 2015; Heidmann, de Lange, Lambalk, Angenent, & Boutilier, 2011; Lutz, Azhagiri, & Maliga, 2011). …”

Azacitidine (5-AzaC)-treatment and mutations in DNA methylase genes affect embryogenic response and expression of the genes that are involved in somatic embryogenesis in Arabidopsis

“…Similarly, the significant up-regulation of the genes that are located in the euchromatin was reported in an ddc mutant ) and the induction of the dd seedling explants on the auxin medium resulted in a continuous increase of the BBM expression that was followed by accelerated callus production (Jiang et al 2015). Relevant to the up-regulated expression of LEC1, LEC2 and BBM in the dd/ddc mutant cultures with an increased SE response, the overexpression of these TFs was demonstrated to be sufficient to induce SE in Arabidopsis (Lotan et al 1998;Stone et al 2001;Boutilier et al 2002) and other plants (Heidmann et al 2011;Guo et al 2013). Collectively, the contrasting expression level of the LEC1, LEC2 and BBM genes, in particular BBM, a positive regulator of LEC1 and LEC2 during SE induction (Horstman et al 2017), which was found in the dd/ddc versus 5-AzaC-treated cultures might account for the opposite embryogenic capacity of these cultures.…”

Polyamines and WOX genes in the recalcitrance to plant conversion of somatic embryos of Habanero pepper (Capsicum chinense Jacq.)

“…The morphogenetic potential of Capsicum sp. has been reported earlier, but the process of regeneration is slow and generally produces low frequencies of shoot regeneration, thus it has been found to be highly recalcitrant (Heidmann et al, 2011;Kothari et al, 2010;Us-Camas et al, 2014). Development of a specific body plan during embryogenesis requires the coordination of cell fates according to their positions along the embryo axes (Breuninger et al, 2008).…”

“…The absence of a functional shoot and the embryo incapacity to convert into plants is how the recalcitrance in Capsisum sp. manifests (Aboshama, 2011;Heidmann et al, 2011;Kothari et al, 2010;Us-Camas et al, 2014).…”