Chlorophyll Breakdown in Senescent Banana Leaves: Catabolism Reprogrammed for Biosynthesis of Persistent Blue Fluorescent Tetrapyrroles

Abstract

Chlorophyll breakdown is a visual phenomenon of leaf senescence and fruit ripening. It leads to the formation of colorless chlorophyll catabolites, a group of (chlorophyll-derived bilin-type) linear tetrapyrroles. Here, analysis and structure elucidation of the chlorophyll breakdown products in leaves of banana (Musa acuminata) is reported. In senescent leaves of this monocot all chlorophyll catabolites identified were hypermodified fluorescent chlorophyll catabolites (hmFCCs). Surprisingly, nonfluorescent chlorophyll catabolites (NCCs) were not found, the often abundant and apparently typical final chlorophyll breakdown products in senescent leaves. As a rule, FCCs exist only fleetingly, and they isomerize rapidly to NCCs in the senescent plant cell. Amazingly, in the leaves of banana plants, persistent hmFCCs were identified that accounted for about 80 % of the chlorophyll broken down, and yellow leaves of M. acuminata display a strong blue luminescence. The structures of eight hmFCCs from banana leaves were analyzed by spectroscopic means. The massive accumulation of the hmFCCs in banana leaves, and their functional group characteristics, indicate a chlorophyll breakdown path, the downstream transformations of which are entirely reprogrammed towards the generation of persistent and blue fluorescent FCCs. As expressed earlier in related studies, the present findings call for attention, as to still elusive biological roles of these linear tetrapyrroles.

Programmed cell death in plants: A chloroplastic connection

“…13,19 Chlorophyll break down leading to yellowing of leaves is one of the signatures of senescence that is believed to be a type of PCD. 22 Similarly chlorophyll catabolism is also observed during biotic and abiotic interactions. 23 Further evidence of light dependent ROS generation from chloroplasts during some HR induced cell death comes from HR induction in Arabidopsis following the interaction with Turnip crinkle virus.…”

Hydrogen sulfide delays leaf yellowing of stored water spinach (Ipomoea aquatica) during dark-induced senescence by delaying chlorophyll breakdown, maintaining energy status and increasing antioxidative capacity

“…The early steps of chlorophyll degradation include the removal of phytol and the formation of chlorophllide a (Chlide a) by chlorophyllase (Chlase), followed by the removal of an Mg atom by either Mgdechelatase (MD) or another Mg-dechelating substance (MDS). Finally, pheophorbide a (Pheide a) is degraded to fluorescent chlorophyll catabolites, which are primarily colorless catabolites (Vergeiner et al, 2013). In this study, we preliminarily investigated the effects of NaHS treatment on activities of Chlase, MD, and MDS.…”

Novel Types of Hypermodified Fluorescent Phyllobilins from Breakdown of Chlorophyll in Senescent Leaves of Grapevine (Vitis vinifera)

“…[12a, 27] Twoa nomeric versionso ft he hmFCC 3 2 OH-O12 4 -Glcepi-pFCC were found (as Ma-FCC-63 and Ma-FCC-64) in extracts of the banana leaves. [27] Esterification of the propionic acid group of FCCs inhibits their acid-induced isomerizationt ot he correspondingN CCs. Hence, it makes hmFCCs persistent, and hmFCCs tend to accumulate in senescent leaves.…”