Radiolabelling of Chlorophyll for Studies on Catabolism

https://doi.org/10.1016/S0176-1617(11)80211-7Get rights and content

Summary

A technique for specifically radiolabelling chlorophyll (ChI) during greening of etiolated barley seedlings is described. Both detached shoots and intact seedlings were employed. Shoots were pretreated with gabaculine, an inhibitor of the reversible δ-aminolaevulinic acid (ALA)-synthesizing transaminase, and then exposed to low light levels in the presence of 4[l4C]-ALA. Radioactivity in ALA labelled in the 4-position is locked into the pyrrol rings of porphyrin. Under these circumstances 80–90 % of the total label incorporated during greening was soluble in 80 % acetone and of the acetone-soluble radioactivity over 70 % was extractable with hexane and recovered in ChI a and b. The feeding of ALA via the rootlets of whole seedlings yielded the same pattern of labelling. It did not require the presence of gabaculine and was associated with a better reproducibility of uptake and total incorporation of radioactivity than experiments with detached shoots. Upon the induction of senescence radioactivity gradually disappeared from the Chls and appeared in a number of polar compounds. Two of them turned out to be identical with putative non-green catabolites described earlier.

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