CRISPR/Cas-mediated in planta gene targeting: current advances and challenges.

Gene targeting can be used to make modifications at a specific region in a plant's genome and create high-precision tools for plant biotechnology and breeding. However, its low efficiency is a major barrier to its use in plants. The discovery of CRISPR (clustered regularly interspaced short palindromic repeats)-Cas-based site-specific nucleases capable of inducing double-strand breaks in desired loci resulted in the development of novel approaches for plant gene targeting.

The immune repressor BIR1 contributes to antiviral defense and undergoes transcriptional and post-transcriptional regulation during viral infections.

BIR1 is a receptor-like kinase that functions as a negative regulator of basal immunity and cell death in Arabidopsis. Using Arabidopsis thaliana and Tobacco rattle virus (TRV), we investigate the antiviral role of BIR1, the molecular mechanisms of BIR1 gene expression regulation during viral infections, and the effects of BIR1 overexpression on plant immunity and development. We found that SA acts as a signal molecule for BIR1 activation during infection.

Tobacco rattle virus 16K silencing suppressor binds ARGONAUTE 4 and inhibits formation of RNA silencing complexes.

The cysteine-rich 16K protein of tobacco rattle virus (TRV), the type member of the genus Tobravirus, is known to suppress RNA silencing. However, the mechanism of action of the 16K suppressor is not well understood. In this study, we used a GFP-based sensor strategy and an Agrobacterium-mediated transient assay in Nicotiana benthamiana to show that 16K was unable to inhibit the activity of existing small interfering RNA (siRNA)- and microRNA (miRNA)-programmed RNA-induced silencing effector complexes (RISCs).

Activation of senescence-associated Dark-inducible (DIN) genes during infection contributes to enhanced susceptibility to plant viruses.

Virus infections in plants cause changes in host gene expression that are common to other environmental stresses. In this work, we found extensive overlap in the transcriptional responses between Arabidopsis thaliana plants infected with Tobacco rattle virus (TRV) and plants undergoing senescence. This is exemplified by the up-regulation during infection of several senescence-associated Dark-inducible (DIN) genes, including AtDIN1 (Senescence 1, SEN1), AtDIN6 (Asparagine synthetase 1, AtASN1) and AtDIN11.