Vacuolar processing enzyme (VPE) is a cysteine protease responsible for vacuolar proteins’ maturation and regulation of programmed cell death (PCD). Four isoforms of Arabidopsis thaliana VPEs were identified previously, but only the functions of βVPE, γVPE, and δVPE were determined. The specific function of a gene is linked to the cis-acting elements in the promoter region. A promoter analysis found repetitive drought-related cis-elements in αVPE, which highlight its potential involvement in drought regulation in A. thaliana. The further co-expression network portraying genes interacting with αVPE substantiated its drought-regulation-related function. Expression of αVPE was upregulated after drought treatment in A. thaliana. To confirm the role of αVPE, a loss of function study revealed that αVPE knockout mutants remained green compared with WT after drought treatment. The mutants had reduced proline activity, decreased sucrose content, and lower MDA content, but increased photosynthetic pigments, indicating that αVPE negatively regulates drought tolerance in A. thaliana. Taken together, our findings serve as important evidence of the involvement of αVPE in modulating drought tolerance in A. thaliana.

The global demand for high-quality crops is continuously growing with time. Crop improvement techniques have a long history and they had been applied since the beginning of domestication of the first agricultural plants. Since then, various new techniques have and are being developed to further increase the commercial value and yield of crops. The latest crop improvement technique known as genome editing is a technique that enables precise modification of the plant genome via knocking out undesirable genes or enabling genes to gain new function. The variants generated from the genome editing are indistinguishable from naturally occurring variation. It is also less time-consuming and more readily accepted in the market commercially. The usage of genome editing has proven to be advantages and plays a promising role in future crop improvement efforts. Therefore, in this chapter, we aim to highlight the progress and application of genome editing techniques, in particular, the CRISPR/Cas9 system as a powerful genome editing tool for crop improvement. In addition, the challenges and future prospects of this technology for crop improvement will also be discussed.