The sonication-assisted whisker method enables CRISPR-Cas9 ribonucleoprotein delivery to induce genome editing in rice

Abstract CRISPR/Cas9-based genome editing represents an unprecedented potential for plant breeding. Unlike animal cells, plant cells contain a rigid cell wall, genome editing tool delivery into plant cells is thus challenging. In particular, the delivery of the Cas9-gRNA ribonucleoprotein (RNP) into plant cells is desired since the transgene insertion into the genome should be avoided for industrial applications in plants. In this study, we present a novel RNP delivery approach in rice. We applied the sonication-assisted whisker method, conventionally developed for DNA delivery in plants, for RNP delivery in rice. Combined with marker gene delivery, we successfully isolated Os LCYβ genome-edited lines generated by RNPs. The calli and regenerated shoot of the Os LCYβ mutant showed abnormal carotenoid accumulation. In addition, we also detected, although at a low frequency, genome editing events in rice calli cells by RNP delivery using the sonication-assisted whisker method without any additional. Therefore, the sonication-assisted whisker method could be an attractive way to create RNP-based genome-edited lines in plants

A vacuolar sorting receptor-independent sorting mechanism for storage vacuoles in soybean seeds

The seed storage proteins of soybean (Glycine max) are composed mainly of glycinin (11S globulin) and β-conglycinin (7S globulin). The subunits of glycinin (A1aB1b, A1bB2, A2B1a, A3B4, and A5A4B3) are synthesized as a single polypeptide precursor. These precursors are assembled into trimers with a random combination of subunits in the endoplasmic reticulum, and are sorted to the protein storage vacuoles. Proteins destined for transport to protein storage vacuoles possess a vacuolar sorting determinant, and in this regard, the A1aB1b subunit contains a C-terminal peptide that is sufficient for its sorting to protein storage vacuoles. The A3B4 subunit, however, lacks a corresponding C-terminal sorting determinant. In this study, we found that, unlike the A1aB1b subunit, the A3B4 subunit does not bind to previously reported vacuolar sorting receptors. Despite this difference, we observed that the A3B4 subunit is sorted to protein storage vacuoles in a transgenic soybean line expressing the A3B4 subunit of glycinin. These results indicate that a protein storage vacuolar sorting mechanism that functions independently of the known vacuolar sorting receptors in seeds might be present in soybean seeds

Efficient production of transgenic soybean (Glycine max [L] Merrill) plants mediated via whisker-supersonic (WSS) method

The present study was designed to evaluate the transformation efficiency and proof the capability of whisker supersonic (WSS) method as an alternative option for soybean (Glycine max [L] Merrill) transformation. We compared soybean transformation efficiency obtained by WSS-mediated with that of particle bombardment transformation by carrying out molecular analysis of the T 0 plants in two independent experiments. For this, we used for both transformation techniques the same genotype, the same plasmid and the same selection method. To assess the efficiency of soybean genetic transformation, we evaluated the efficiency of multi gene transformation by the selection with hygromycin and the expression of green fluorescent protein [sGFP (S65T)] resulted from both techniques. Regenerable embryogenic cells were induced from immature cotyledons of soybean c.v Jack on MSD40 media within 3 weeks then proliferated on FN lite liquid media and engineered with pUHG gene construct through both WSS and particle bombardment-mediated transformation. The pUHG was constructed with pUC 19 and contain the hpt gene conferring resistance to hygromycin as a selective marker and sGFP(S65T) as a reporter gene. Fluorescence microscopy screening after the selection of hygromycin, identified the clearly expression of sGFP(S65T) in the transformed soybean embryos. Stable integration of the transgenes was confirmed by polymerase chain reaction (PCR) and Southern blot analysis. The average transformation efficiency achieved with WSS was higher than that obtained by particle bombardment and hence it may represent an alternative method for soybean transformation

Successful Production of Offspring Derived from Phospholipase C Zeta-Deficient Sperm by Additional Artificial Activation

During mammalian fertilization, repetitive rises of intracellular calcium called calcium oscillations are required for full activation of oocytes. Therefore, oocytes such as round spermatid injected or somatic cell nuclear transferred require additional artificial activation which mimics the calcium oscillations. It is well recognized that sperm specific phospholipase C (PLCζ) is a strong candidate as the sperm factor which can induce calcium oscillations and, at least in mammals, the genetic mutation of PLCζ in human causes male infertility due to the lack of calcium oscillations in the oocytes. Recent studies showed that the sperm lacking PLCζ (Plcz1−/−) still could induce rise(s) of intracellular calcium in the oocytes after IVF but not intracytoplasmic sperm injection (ICSI). In the ICSI oocytes, no pronuclear formation or development to the two-cell stage was observed. However, it is still unclear whether additional activation treatment can rescue the low developmental ability of Plcz1−/−-sperm-derived oocytes after ICSI. In this study, we examined whether oocytes injected with a Plcz1−/− sperm can develop to term by additional artificial activation. In oocytes injected a Plcz1−/− sperm and Plcz1−/− and eCS (another candidate of the sperm factor) double knockout sperm (Plcz1−/−eCS−/−), the rates of pronuclear formation were very low (2.0 ± 2.3% and 6.1 ± 3.7%, respectively) compared to control (92.1 ± 2.6%). However, these rates were dramatically improved by additional procedures of PLCζ-mRNA injection or SrCl2 treatment (Plcz1−/− sperm + PLCζ mRNA, Plcz1−/− sperm + SrCl2 and Plcz1−/−eCS−/− sperm + PLCζ mRNA; 64.2 ± 10.8%, 89.2 ± 2.4% and 72.6 ± 5.4%, respectively). Most of the oocytes were developed to the two-cell stage. After embryo transfer, healthy pups were obtained in all these groups (Plcz1−/− sperm + PLCζ mRNA:10.0 ± 2.8%, Plcz1−/− sperm + SrCl2:4.0 ± 4.3% and Plcz1−/−eCS−/− sperm + PLCζ mRNA: 10.0 ± 5.7%). The rate in Plcz1−/− sperm + SrCl2 group was significantly lower than that in control (26.0 ± 2.4%). Taken together, our present results show that additional activation treatment such as SrCl2 and PLCζ mRNA can fully support to develop to term even in oocyte injected Plcz1−/− sperm. In addition, PLCζ-induced oocyte activation is more suitable for successful development to term compared to that such as phenomenon induced by SrCl2. These findings will contribute to improvement for male-dependent human infertility and reproductive technologies in other mammalian species