Differential ُExpression of RuBisCO large Subunit and its Assembly in Intact Chloroplasts of Pisum sativum L. Treated with NaCl and Jasmonic Acid

Abstract

This study aimed to detect the effect of stress conditions imposed by different treatments NaCl and jasmonic acid (JA) on the expression pattern and assembly of RuBisCO large subunit (RbcL) and RuBisCO enzyme complex using SDS-PAGE and HDN-PAGE techniques, respectively. Both TSPs and ChPs were variably affected by each treatment. Notably, a unique protein band was detected in the seedlings treated with 150 mM NaCl for 5 days. Surprisingly, this band was not detected under any other salt treatment. Using nano HPLC-ESI-MS/MS MALDI-TOF protein sequencing, this band was identified as downshifted RbcL at approximately 50 kDa in addition to the original one at approximately 55 kDa. The expression of RbcL protein decreased in a dose dependent manner in the plants treated with JA for one and five days. All treatments did not affect the RuBisCO complex assembly at approximately 660 kDa, but triggered stress-induced ChPs at approximately 440 kDa and 1 MDa concomitant with NaCl treatments. RbcL band isolated from intact chloroplast was associated with Coupling Factor (CF1) beta subunit of ATP synthase as revealed by MALDI-TOF protein sequencing analysis. Possible interpretations of these findings have been further discussed in this study.