After flower pollination, a programmed process called abscission occurs in which unwanted floral organs are actively shed from the main plant body. We found that a member of the DOF (for DNA binding with one finger) transcription factor family, Arabidopsis (Arabidopsis thaliana) DOF4.7, was expressed robustly in the abscission zone. The Arabidopsis 35S::AtDOF4.7 lines with constitutive expression of AtDOF4.7 exhibited an ethylene-independent floral organ abscission deficiency. In these lines, anatomical analyses showed that the formation of the abscission zone was normal. However, dissolution of the middle lamella failed to separate between the cell walls. AtDOF4.7 was identified as a nucleus-localized transcription factor. This protein had both in vitro and in vivo binding activity to typical DOF cis-elements in the promoter of an abscission-related polygalacturonase (PG) gene, PGAZAT. Overexpression of AtDOF4.7 resulted in down-regulation of PGAZAT. AtDOF4.7 interacted with another abscission-related transcription factor, Arabidopsis ZINC FINGER PROTEIN2. Taken together, our results suggest that AtDOF4.7 participates in the control of abscission as part of the transcription complex that directly regulates the expression of cell wall hydrolysis enzymes.

The CRISPR‐ Streptococcus pyogenes Cas9 (SpCas9) system offers a rapid, simple and flexible genome editing approach. However, the targeting scope of the SpCas9 system is limited by the canonical NGG PAM. To broaden the editing range of the CRISPR system, several Cas orthologs recognized different PAM were isolated from diverse microbes and were engineered as powerful genome editing tools in eukaryotic cells (Murovec et al., 2017). One Cas9 ortholog, Staphylococcus aureus Cas9 (SaCas9), has a smaller size and comparable activity compared to SpCas9 (Kleinstiver et al., 2015a; Kleinstiver et al., 2015b). Previous studies reported that the SaCas9 could induce highly efficient targeted mutagenesis in Arabidopsis, citrus, tobacco and rice (Murovec et al., 2017).

CRISPR/Cas9 is an adaptive immunity system in bacteria and most archaea ( Koonin and Makarova, 2009; Horvath and Barrangou, 2010). The CRISPR/Cas9 gene editing system is comprised of two key components, a small guide RNA (gRNA) and a Cas9 endonuclease ( Deltcheva et al., 2011; Jinek et al., 2012). The gRNA is a chimeric RNA molecule of tracrRNA and crRNA ( Ran et al., 2013) which guides the Cas9 protein to the target site in the genome. Therefore, selecting a target site with high on-target activity and low off-target effect is crucial for gene editing. Previously, we have discovered that the gene editing activity of CRISPR-Cas9 in mammalian cells was affected by several factors, such as the secondary structure and chromatin accessibility of the guide sequences ( Jensen et al., 2017). Strikingly, previous results from us and other research groups consistently revealed that the CRISPR gRNA activities are highly variable. Thus, several in silico gRNA design web tools and algorithms have been developed to facilitate CRISPR design and applications.

It has been demonstrated that lignin was efficiently degraded by Lentinula edodes (L. edodes). However, the process of lignin degradation and utilization by L. edodes has not been discussed in detail. Therefore, the effects of lignin on L. edodes mycelium growth, chemical compositions, and phenolic profiles were investigated herein. It has been revealed that 0.10% lignin acted as the most effective concentration to accelerate mycelia growth, which yielded the highest biomass of 5.32 ± 0.07 g/L. Furthermore, a 0.10% concentration of lignin promoted the accumulation of phenolic compounds, especially protocatechuic acid, with peak value of 48.5 ± 1.2 μg/g. In contrast, the higher concentration of lignin (0.20%) exerted an inhibitory effect on the growth of L. edodes. Overall, the application of lignin at the optimal concentration of 0.10% could not only enhance the mycelial growth but also accumulate the phenolic acids and raise the nutritional and medical values of L. edodes.