A key to totipotency: Wuschel‐like homeobox 2a unlocks embryogenic culture response in maize (Zea mays L.)

Abstract

SummaryThe ability of plant somatic cells to dedifferentiate, form somatic embryos and regenerate whole plants in vitro has been harnessed for both clonal propagation and as a key component of plant genetic engineering systems. Embryogenic culture response is significantly limited, however, by plant genotype in most species. This impedes advancements in both plant transformation‐based functional genomics research and crop improvement efforts. We utilized natural variation among maize inbred lines to genetically map somatic embryo generation potential in tissue culture and identify candidate genes underlying totipotency. Using a series of maize lines derived from crosses involving the culturable parent A188 and the non‐responsive parent B73, we identified a region on chromosome 3 associated with embryogenic culture response and focused on three candidate genes within the region based on genetic position and expression pattern. Two candidate genes showed no effect when ectopically expressed in B73, but the gene Wox2a was found to induce somatic embryogenesis and embryogenic callus proliferation. Transgenic B73 cells with strong constitutive expression of the B73 and A188 coding sequences of Wox2a were found to produce somatic embryos at similar frequencies, demonstrating that sufficient expression of either allele could rescue the embryogenic culture phenotype. Transgenic B73 plants were regenerated from the somatic embryos without chemical selection and no pleiotropic effects were observed in the Wox2a overexpression lines in the regenerated T0 plants or in the two independent events which produced T1 progeny. In addition to linking natural variation in tissue culture response to Wox2a, our data support the utility of Wox2a in enabling transformation of recalcitrant genotypes.

Genome-Wide Association Studies of Embryogenic Callus Induction Rate in Peanut (Arachis hypogaea L.)

“…To date, many studies have been conducted on genes associated with embryogenic callus induction in plants [35][36][37]. In the present study, several significant SNPs merit discussion in detail (Table 2).…”

Appreciating animal induced pluripotent stem cells to shape plant cell reprogramming strategies

“…Subsequent overexpression of WOX2 improved somatic embryo formation in recalcitrant inbred lines. Importantly, WOX2 overexpression lines did not display aberrant phenotypes, which is beneficial for its application, but also suggests the involvement of additional factors during the reprogramming at the immature embryo explant stage ( McFarland et al , 2023 ).…”

Multifaceted roles of transcription factors during plant embryogenesis

“…Three different barrel clover lines were used to test the effects of overexpression of MtWOX9-1 using leaves as the explants and the results showed MtWOX9-1 promoted somatic embryogenesis as well as led to the expression changes of two embryogenesis-associated MADS-box genes ( Tvorogova et al., 2019 ). Similarly, WOX2a promotes somatic embryogenesis in recalcitrant maize genotypes ( Mcfarland et al., 2023 ). Overexpression of the WOX2a gene from an embryogenic maize genotype A188 produced somatic embryos from a recalcitrant genotype B73.…”