CaSK23, a Putative GSK3/SHAGGY-Like Kinase of

Area of Science:

• Plant molecular biology
• Plant immunity
• Plant signaling pathways

Background:

• GSK3-like kinases are involved in brassinosteroid pathways, affecting plant growth and stress responses.
• Their specific roles in plant immunity are not well understood.
• CaSK23 is a GSK3-like kinase identified in pepper plants.

Purpose of the Study:

• To investigate the role of CaSK23 in pepper's immune response to Ralstonia solanacearum.
• To determine if CaSK23 acts as a positive or negative regulator in plant immunity.

Main Methods:

• Quantitative RT-PCR (qRT-PCR) to analyze CaSK23 expression levels.
• Virus-induced gene silencing (VIGS) to knock down CaSK23 expression in pepper.
• Ectopic overexpression (OE) of CaSK23 in tobacco plants.
• Transient overexpression of CaSK23 in pepper plants.

Main Results:

• CaSK23 expression decreased upon Ralstonia solanacearum inoculation and treatment with salicylic acid or methyl jasmonate.
• Silencing CaSK23 enhanced pepper resistance to Ralstonia solanacearum, up-regulating defense genes.
• Overexpression of CaSK23 in tobacco and pepper compromised resistance and down-regulated defense genes.

Conclusions:

• CaSK23 acts as a negative regulator of pepper immunity against Ralstonia solanacearum.
• Constitutive CaSK23 expression suppresses basal immunity, while its downregulation upon pathogen attack derepresses defense mechanisms.