Protein phosphorylation regulates in vitro spinach chloroplast petD mRNA 3′-untranslated region stability, processing, and degradation

► A spinach chloroplast mRNA 3′-UTR processing extract (CPE) processes or stabilizes petD, depending on ATP concentration. ► A dephosphorylated CPE degrades petD and recovers 3′-UTR processing/stabilization in an ATP concentration dependent manner. ► 24RNP and 28RNP CPE proteins are essential to prevent petD degradation, and mediate 3′-UTR processing and stability. ► Phosphorylation of 24RNP, 28RNP and other CPE proteins regulates petD mRNA stability, 3′-UTR processing and degradation. ► Protein phosphorylation might be a mechanism regulating chloroplast mRNA metabolism in vivo.