Replication of a geminivirus derived shuttle vector in maize endosperm cells

Area of Science:

• Plant molecular biology
• Virology
• Genetic engineering

Background:

• Maize (Zea mays L.) endosperm cell cultures support replication of wheat dwarf virus (WDV) DNA.
• Understanding viral replication sequences is crucial for developing plant gene expression vectors.

Purpose of the Study:

• To analyze DNA sequences essential for WDV replication.
• To create a versatile plant gene expression vector for maize endosperm cells.
• To establish a selectable marker system for both plant and bacterial hosts.

Main Methods:

• Development of a 3.7 kb Escherichia coli-plant shuttle vector, pWI-11, incorporating WDV replication origins.
• Replacement of the WDV coat protein gene with the neomycin phosphotransferase II (NPT II) gene for selectable marker function.
• Introduction of a beta-glucuronidase (GUS) reporter gene under the cauliflower mosaic virus 35S promoter.
• Transformation of maize endosperm protoplasts with pWI-11 and subsequent analysis of replication and gene expression.

Main Results:

• The pWI-11 vector successfully replicated in maize endosperm cells.
• High-level expression of the GUS reporter gene was observed in transformed maize cells.
• Replicating viral DNA was rescued from maize cells by E. coli transformation using kanamycin selection.
• GUS expression levels correlated with viral sequence replication over time.

Conclusions:

• The pWI-11 shuttle vector is effective for replication and gene expression in maize endosperm cells.
• The NPT II gene fusion serves as a reliable selectable marker in both plant and bacterial systems.
• This system provides a valuable tool for studying geminivirus replication and for plant genetic engineering applications.