Efficient Agrobacterium-mediated in planta genetic transformation of watermelon [Citrullus lanatus Thunb.]

A comprehensive review of in planta stable transformation strategies

Plant transformation remains a major bottleneck to the improvement of plant science, both on fundamental and practical levels. The recalcitrant nature of most commercial and minor crops to genetic transformation slows scientific progress for a large range of crops that are essential for food security on a global scale. Over the years, novel stable transformation strategies loosely grouped under the term "in planta" have been proposed and validated in a large number of model (e.g. Arabidopsis and rice), major (e.g. wheat and soybean) and minor (e.g. chickpea and lablab bean) species. The in planta approach is revolutionary as it is considered genotype-independent, technically simple (i.e. devoid of or with minimal tissue culture steps), affordable, and easy to implement in a broad range of experimental settings. In this article, we reviewed and categorized over 300 research articles, patents, theses, and videos demonstrating the applicability of different in planta transformation strategies in 105 different genera across 139 plant species. To support this review process, we propose a classification system for the in planta techniques based on five categories and a new nomenclature for more than 30 different in planta techniques. In complement to this, we clarified some grey areas regarding the in planta conceptual framework and provided insights regarding the past, current, and future scientific impacts of these techniques. To support the diffusion of this concept across the community, this review article will serve as an introductory point for an online compendium about in planta transformation strategies that will be available to all scientists. By expanding our knowledge about in planta transformation, we can find innovative approaches to unlock the full potential of plants, support the growth of scientific knowledge, and stimulate an equitable development of plant research in all countries and institutions.

Overexpression of AtMYB12 transcription factor simultaneously enhances quercetin-dependent metabolites in radish callus

The study aimed to enhance quercetin production in radish by optimizing Agrobacterium tumefaciens-mediated in-planta transformation. This protocol involved infecting radish seed embryo axis with A. tumefaciens EHA105 strain carrying the 35S::AtMYB12. Radish seeds were infected with the Agrobacterium suspension (0.8 OD600) for 30 min, followed by sonication for 60 s and vacuum infiltration for 90 s at 100 mm Hg. A 3-day co-cultivation in Murashige and Skoog medium with 150 μM acetosyringone yielded a transformation efficiency of 59.6% and a transgenic callus induction rate of 32.3%. Transgenic plant and callus lines were confirmed by GUS histochemical assay, PCR, and qRT-PCR. The transgenic lines showed an increased expression of flavonoid pathway genes (AtMYB12, CHS, F3H, and FLS) and antioxidant genes (GPX, APX, CAT, and SOD) compared to WT plants. Overexpression of AtMYB12 in transgenic callus increased enzyme activity of phenylalanine ammonia lyase, catalase, and ascorbate peroxidase. In half-strength MS medium with 116.8 mM sucrose, the highest growth index (7.63) was achieved after 20 days. In AtMYB12 overexpressed callus lines, phenolic content (357.31 mg g-1 dry weight), flavonoid content (463 mg g-1 dry weight), and quercetin content (48.24 mg g-1 dry weight) increased significantly by 9.41-fold. Micro-wounding, sonication, and vacuum infiltration improved in-planta transformation in radishes. These high-quercetin-content transgenic callus lines hold promise as valuable sources of flavonoids.