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

Abstract

a b s t r a c tColorless, non-fluorescent Chl-catabolites (NCCs) are the typical, ubiquitous products of chlorophyll (Chl)-breakdown in senescent leaves. However, a fluorescent Chl-catabolite (FCC) accumulated in de-greened leaves of Spathiphyllum wallisii (Peace Lily), which showed a weak blue luminescence. The FCC, named Sw-FCC-62, was 'hypermodified' with an unprecedented 6-(2-[3,4-dihydroxy-phenyl]-ethyl)-b-glucopyranosidyl ester at the propionyl group. Such esters stabilize FCCs against their typical and rapid, spontaneous isomerization to NCCs. Chl-breakdown in Sp. wallisii thus branches off from the 'common' path in leaves, and furnishes unique and 'persistent' FCCs. Our findings on 'hypermodified' FCCs also call for attention as to possible physiological roles of Chl-catabolites in plants.

Update on the biochemistry of chlorophyll breakdown

“…Hypermodified FCCs New types of FCCs, termed hypermodified FCCs (hFCCs) were recently identified in ripening banana fruits and in senescent banana and peace lily leaves Moser et al 2008aMoser et al , 2009Kräutler et al 2010). In contrast to the transient occurrence of mFCCs as intermediary catabolites in senescing leaves that are converted to NCCs (see above), hFCCs persist in ripening or senescing tissues.…”

Stereo‐ and Regioselective Phyllobilane Oxidation in Leaf Homogenates of the Peace Lily (Spathiphyllum wallisii): Hypothetical Endogenous Path to Yellow Chlorophyll Catabolites

“…wallisii leaves at ambient temperature and analysis by HPLC indicated the presence of several (minor) fractions with UV/Vis-absorption characteristics typical of NCCs, as well as of a major "fluorescent" CC (FCC), named . [9] The least polar among the NCCs, named Sw-NCC-58 (4), [9] was characterized as a 1-formyl-3 2 -hydroxy- 19-oxo-16n-16,19-dihydrophyllobilane (for nomenclature and atom numbering see Experimental Section, Figure 7). In addition, several other presumed CCs were indicated, such as the polar NCCs 5 and 6, and the "yellow" CC (YCC) 7.…”

“…[8] A sample of 370 nmol (250 mg) of the slightly more polar fraction of the NCC Sw-NCC-51 (5) was also isolated, whose UV and CD spectra (see Supporting Information,Figure S1) were similar to those of 4. [9] When analyzed by positive ion ESI-mass spectrometry, pseudo-molecular ions [M+K] + and [M+H] + were found at m/z 713.3 and m/z 675.4, respectively, consistent with a molecular formula of 5 of C 36 H 42 N 4 O 9 (indicating the formal addition of a CH 2 O unit to 4). Fragments at m/z 643.3 and 611.2 showed loss of one and of two units of methanol, and a fragment at m/z 552.2 suggested loss of ring D (C 7 H 9 NO) (see Figure 2).…”

“…This finding was thus consistent with our earlier assignment of 4 (from Sp. wallisii) [9] as C16-epimer of 4epi (from Cercidiphyllum japonicum). [16] iii) Preparation of 5epi and of 6epi via oxidation of 4epi with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)…”

“…These (C16)-epimeric pFCCs are mostly short lived and isomerize rapidly in (weakly acidic) aqueous medium to the corresponding NCCs, whose newly formed saturated C10 was assigned R configuration, based on the mechanistic analysis of their highly stereoselective isomerization process. [7] However, in yellow senescent leaves of banana plants (Musa acuminata), [8] and of the Peace Lily (Spathiphyllum wallisii), [9] persistent, "hyper-modified fluorescent" CCs (hmFCCs) accumulated, whereas NCCs either appeared to be completely absent (banana leaves [8] ), or they were apparently found only in small amounts (Peace Lily leaves [9] ). Persistent hmFCCs are sources of remarkable "fluorescence" signals [10] and effective sensitizers of the endogenous, light-induced formation of singlet oxygen ( 1 O 2 ), [11] and may have further biological roles in plants.…”