A geminivirus-induced gene silencing system for gene function validation in cassava

Area of Science:

• Plant molecular biology
• Functional genomics
• Crop science

Background:

• Cassava (Manihot esculenta) gene function analysis is crucial for crop improvement.
• Existing methods for gene suppression in cassava have limitations.
• Virus-induced gene silencing (VIGS) offers a potential alternative for rapid gene function studies.

Purpose of the Study:

• To develop and validate an African cassava mosaic virus (ACMV) based VIGS system for gene silencing in cassava.
• To assess the efficiency of the ACMV VIGS system in down-regulating endogenous cassava genes.
• To compare the efficacy of VIGS with transgenic approaches for suppressing a specific biosynthetic pathway.

Main Methods:

• Construction of an ACMV-based gene-silencing vector containing fragments of the Nicotiana tabacum sulfur (su) gene and cassava CYP79D2 gene.
• Induction of gene silencing in cassava plants via the ACMV vector.
• Quantification of linamarin content in silenced cassava leaves.
• Comparison of VIGS results with previously published data from transgenic approaches.

Main Results:

• The ACMV-VIGS vector successfully induced silencing of the orthologous cassava sulfur gene, indicated by yellow-white leaf spots.
• Silencing of cassava CYP79D1 and CYP79D2 genes using the ACMV vector led to an 76% reduction in linamarin content at 21 days post-inoculation.
• The ACMV VIGS system demonstrated comparable efficiency to transgenic methods in suppressing the linamarin biosynthetic pathway.

Conclusions:

• The ACMV-based VIGS system is a viable and effective tool for gene function analysis in cassava.
• VIGS provides a valuable complement or alternative to transgenic approaches for gene discovery and pathway suppression in cassava.
• Leveraging sequence databases from model plants is beneficial for functional genomics in non-model crops like cassava.