The effect of phytosulfokine alpha on haploid embryogenesis and gene expression of Brassica napus microspore cultures

Advances and Challenges in Haploid Induction for Warm-Season Legumes

Haploid induction via doubled haploid (DH) technology is pivotal for achieving true homozygosity in plant breeding; however, Fabaceae species lag in establishing effective haploidization methods. This review explores recent advances in DH techniques for warm-season legumes, including soybean, cowpea, pigeon pea, common bean, peanut, mung bean, and winged bean, highlighting key challenges and perspectives. While anther culture, cold pretreatment, and MS-based medium with growth regulators demonstrate potential, fully reproducible protocols remain elusive. Advances in microspore-derived embryogenesis have improved regeneration consistency in soybeans, cowpeas, and peanuts. Key areas for improving DH technology include optimizing regeneration conditions, such as shortening the callus phase and accelerating embryo and shoot development. Recent advancements in CRISPR/Cas9-mediated genome modifications, targeting genes like CENH3, MTL, and DMP, offer promising strategies to enhance efficiency and overcome resistance to conventional methods. Integrating molecular tools with haploid induction and conventional breeding techniques can significantly improve legume breeding and productivity.

Phytosulfokine alpha enhances regeneration of transformed and untransformed protoplasts of Brassica oleracea

Phytosulfokine-α (PSK-α) is a disulfated pentapeptide (YIYTQ) acting as an intercellular signal peptide and growth factor. It was originally isolated from conditioned medium of asparagus mesophyll cell cultures in 1996 and later characterized as a hormone-like signal molecule with important roles in numerous processes of in vivo plant growth and development. It is currently becoming a valuable mitogenic factor in plant breeding and biotechnology due to its stimulatory effect on in vitro cell elongation, proliferation and differentiation. The focus of our work was to review current knowledge about the roles of PSK-α in plant biotechnology and to evaluate its influence on the regeneration of protoplasts of four Brassica oleracea cultivars (two cauliflower and two cabbage) cultured under two distinctive protocols and with different protoplast densities. Protoplast regeneration was studied due to its high value for plant genome editing, which is generally limited by the inefficient regeneration of treated protoplasts of numerous important plant genotypes. Our hypothesis was that the stress related to PEG-mediated protoplast transformation and the following decrease in viable protoplast density in culture could be alleviated by the addition of PSK-α to the culture medium. We therefore tested whether PSK-α could increase cell division at the early stages of culture (5 and 15 days after protoplast isolation) and stimulate the formation of microcallus colonies up to the 30st day of culture and to evaluate its influence on callus organogenesis leading to shoot regeneration. The PSK-α showed a strong stimulatory effect on untransformed protoplast regeneration already during the first days of culture, accelerating cell division up to 5.3-fold and the formation of multicellular microcallus colonies up to 37.0-fold. The beneficial influence was retained at later stages of regeneration, when PSK improved shoot organogenesis even if it was present only during the first 10 days of culture. The highest numbers of shoots, however, were regenerated when PSK was present during the first days of culture and later in solid shoot regeneration medium. Finally, the addition of PSK-α to PEG-transformed protoplasts significantly enhanced their division rate and the formation of microcallus colonies in selection media, up to 44.0-fold.