Calcium/Calmodulin Regulated Cell Wall Regeneration in Zea mays Mesophyll Protoplasts

Abstract

Abstract The composition of newly synthesized cell walls starting from enzymatically isolated Zea mays mesophyll protoplasts was studied. The contents of pectin, cellulose and hemicellulose in addition to the wall-associated proteins were followed in the presence of increasing con­centrations of calcium ions with or without the calcium channel blockers like lanthanum, lithium ions, verapamil, nifedipine and the calmodulin antagonist trifluperazine. Pectin accu­mulation was inhibited by all antagonists except lanthanum. Cellulose formation, however, was increased by organic antagonists trifluperazine, verapamil and maximally by nifedipine while it was not affected by the inorganic ions lanthanum or lithium. Hemicellulose accumu­ lated with nifedipine present but significantly decreased by all other antagonists. Added Ca2+ (5 -10 mᴍ) reversed most of the blockers-induced inhibition on pectin and hemicellulose. In the case of cellulose, however, calcium concentration which reversed the inhibitory action of these antagonists was dependent on the antagonist. Starch exhibited little alterations indicat­ ing its minor role in deposition of wall components. Cell wall-associated proteins were negatively affected by lanthanum and verapamil and positively by lithium and nifedipine. Gen­erally, this fraction was found in a negative correlation with pectin levels. Chlorophyll contents were lowered after growth for 48 h; this might be due to repeated cell division. These results are discussed in relation to the mechanism of antagonists and effects of calcium.