Hypermodified Fluorescent Chlorophyll Catabolites: Source of Blue Luminescence in Senescent Leaves

Abstract

Yellow leaves of bananas glow blue under UV light. The luminescence is caused by uniquely glycosylated (“hypermodified”) chlorophyll catabolites that accumulate in senescent banana leaves. These findings suggest that (some) chlorophyll catabolites are not mere detoxification products, but are likely to play still unknown physiological roles.

A novel blue fluorescent chlorophyll catabolite accumulates in senescent leaves of the peace lily and indicates a split path of chlorophyll breakdown

“…Related FCCs were found to accumulate and induce blue luminescence in yellow M. acuminata bananas [12], in senescent sections of peels of overripe bananas [14], and in senescent banana leaves [13] (see SuppMat, Fig. S2).…”

“…wallisii (here) and in Musa acuminata [12]. The ester stabilizes FCCs against their (chemical) transformation to NCCs and, possibly, preserving FCCs for an unknown biological role [12][13][14]: The ester function of Sw-FCC-62 is a b-gluco-pyranosyl-(1?1)-2-(3,4-dihydroxyphenyl)-ethyl unit, and belongs to the class of the phenylethyl-glycosides [24][25][26]. Interestingly, phenylethyl-glycosides were known in dicotyls, for which they were suggested to be useful as taxonomic markers [36].…”

“…Few plants are known to have 'visibly' luminescent senescent leaves, e.g., Ginkgo biloba [39] or bananas [13], but FCCs were only detected in the latter. The optical perception of de-greened leaves, fruit (and flowers) helps guide the crucial interactions of plants with insects, birds and other animals (see e.g.…”

“…[40,41]). 'Persistent' FCCs, the newly discovered blue luminescent plant pigments, are sources of optical signals [12][13][14], and may be useful as natural molecular in-vivo markers and signals of ripening and of programmed cell death. .…”

“…The complex signals of 14 additional hydrogen atoms identified a glucopyranose moiety and a 2-(3,4-dihydroxyphenyl)-ethyl unit as peripheral modification of this Sw-FCC, as well as the b-configuration at the anomeric center of the sugar unit. The attachment site of this functionalized glucopyranoside unit at the propionate group of the FCC-core was deduced from a 1 H, 13 Fig. 3).…”