The chloroplast RNA-binding protein CP29A supports rbcL expression during cold acclimation

Area of Science:

• Plant molecular biology
• Photosynthesis research
• Chloroplast gene expression

Background:

• The chloroplast genome encodes essential photosynthetic proteins, including Ribulose-1,5-bisphosphat-carboxylase/-oxygenase (RuBisCo).
• Expression of these genes is mainly regulated post-transcriptionally by nuclear-encoded RNA-binding proteins (RBPs).
• Cold stress challenges plants, often leading to increased RuBisCo production for acclimation, a mechanism not fully understood.

Purpose of the Study:

• To investigate the role of chloroplast RNA-binding protein CP29A in cold acclimation.
• To identify specific RNA binding sites of CP29A at nucleotide resolution.
• To understand CP29A's contribution to the regulation of RuBisCo (rbcL) gene expression under cold conditions.

Main Methods:

• Analysis of CP29A-RNA interactions at nucleotide resolution.
• Generation and analysis of CRISPR/Cas9-induced NtCP29A mutants in tobacco.
• Assessment of rbcL mRNA and RbcL protein levels in wild-type and mutant plants under varying temperatures.

Main Results:

• CP29A preferentially binds to the 5'-untranslated region of rbcL mRNA, downstream of the MRL1 binding site.
• Tobacco mutants lacking NtCP29A displayed significant cold-dependent photosynthetic deficiencies across the leaf blade.
• These deficiencies correlated with reduced rbcL mRNA and RbcL protein accumulation in the mutants.

Conclusions:

• Chloroplast RNA-binding protein CP29A plays a vital role in the cold acclimation of RbcL production.
• CP29A's interaction with rbcL mRNA contributes to maintaining photosynthetic efficiency under low temperatures.
• The findings highlight a key regulatory mechanism for chloroplast gene expression during plant cold stress response.