Stay‐green genotypes of Phaseolus vulgaris L.: chloroplast proteins and chlorophyll catabolites during foliar senescence

Abstract

SUMMARYLeaf senescetYce was analyzed in stay-green mutants of Phaseolus vulgaris. Impaired yellowing in these genotypes was accompanied by abnormal retention of tbylakoid membrane proteins including tbe ligbt-bar\'esting cblorophyll-binding protein of photosystem II, tbe 33 kDa polypeptide of tbe oxygen-evolving complex, cytocbrome/ and tbe psaF protein of pbotosystem I. On tbe other band, ribulose bispbospbate carboxylase was somewbat more labile in tbe mutant than tbe wild-type. Tbe stay-green cbaracter was not associated with unusual persistence of cbloropbyll biosynthesis etizymes. During senescence, normal leaf tissue accunnulated an array of fluorescent (FCC) and non-fluorescent (NCC) compounds witb cbromatograpbic and spectropbotometric properties similar to tbose of cbloropbyll catabolites previously identified in otber species. Witb the exception of one prominent NCC and a trace of one FCC, tbese constituents were absent from extracts of stay-green genotypes, strongly supporting tbe proposal tbat tbey are indeed products of cbloropbyll breakdown. Tbe kinetics of tbeir accumulation during senescence was consistent witb a primary or intermediary role for FCCs in tbe catabolic pathway wbereas NCCs seem to be final products. Tbe complement of FCCs and NCCs in Phaseolus vulgaris was as distinct from that of tbe previously-studied species barley and rape as tbe latter are from each otber. Genotj'pic and interspecific variations in tbe biochemistry of senescence are discussed in relation to genetic regulation of tbe process.

An Evaluation of the Basis and Consequences of a Stay-Green Mutation in thenavel negraCitrus Mutant Using Transcriptomic and Proteomic Profiling and Metabolite Analysis

“…In addition, the proteomic analysis identified rbcL as one of the major proteins with lower abundance in nan (Figs. 5 and 6; Table V), which differs from the results seen with a rice sgr mutant and the retention of Rubisco in leaves of the tomato green flesh mutant (Akhtar et al, 1999) but agrees with the previously observed reduced Rubisco protein levels in a P. vulgaris stay-green mutant (Bachmann et al, 1994). If photosynthetic capacity is insufficient under conditions of excess absorbed light, free Chl can generate ROS, which in turn can cause extensive oxidative damage to the thylakoid membrane (Barber and Andersson, 1992;Niyogi, 1999).…”

“…Those identified to date span a broad taxonomic range, including members of the Gramineae (durum wheat [Triticum durum; Spano et al, 2003]; Festuca pratensis [Thomas, 1987]; rice [Oryza sativa; Cha et al, 2002;Jiang et al, 2007;Kusaba et al, 2007;Park et al, 2007]), Arabidopsis (Arabidopsis thaliana; Woo et al, 2001;Oh et al, 2003Oh et al, , 2004Ren et al, 2007), and the Leguminosae (soybean [Glycine max;Guiamét andGiannibelli, 1994, 1996;Luquez and Guiamét, 2002]; Phaseolus vulgaris [Ronning et al, 1991;Bachmann et al, 1994]; pea [Pisum sativum; Armstead et al, 2007;Sato et al, 2007]). A stay-green mutant phenotype has also been reported in tomato (Solanum lycopersicum) fruits (the green flesh mutant; Cheung et al, 1993;Akhtar et al, 1999) and pepper (Capsicum annuum; mutant chlorophyll retainer; Efrati et al, 2005;Roca and Mínguez-Mosquera, 2006).…”

Stay-green protein, defective in Mendel’s green cotyledon mutant, acts independent and upstream of pheophorbide a oxygenase in the chlorophyll catabolic pathway

“…3A, B). LHCII was fully retained during the course of senescence in JI2775, a feature that has been described in different stay-green mutants (Hilditch et al, 1989;Bachmann et al, 1994;Pružinská et al, 2003;Park et al, 2007), but in contrast to the stay-green mutant Bf993 of Festuca pratensis (Thomas and Howarth, 2000), proteolytic fragments of LHCII could not be detected in JI2775. In addition, core subunits of PSI (PsaD) and PSII (PsbA) were also retained to some extend in the mutant, and degradation of Rubisco subunits was somewhat slower in JI2775 compared to JI4.…”

Breakdown of chlorophyll: A nonenzymatic reaction accounts for the formation of the colorless “nonfluorescent” chlorophyll catabolites

“…1), which accumulate in the vacuoles of senescent leaves (5,6,15). Under conditions where senescenceinduced Chl breakdown occurred with high rates, FCCs were observed temporarily and suggested to be catabolic intermediates preceding the NCCs (29,30).…”