Genome-wide identification and analysis of the SGR gene family in Cucumis melo L.

Abstract

ABSTRACT. Chlorophyll (CHL) is present in many plant organs, and its metabolism is strongly regulated throughout plant development. Understanding the fate of CHL in senescent leaves or during fruit ripening is a complex process. The stay-green (SGR) protein has been shown to affect CHL degradation. In this study, we used the conserved sequences of STAY-GREEN domain protein (NP_567673) in Arabidopsis thaliana as a probe to search SGR family genes in the genome-wide melon protein database. Four candidate SGR family genes were identified in melon (Cucumis melo L. Hetao). The phylogenetic evolution, gene structure, and conserved motifs were subsequently analyzed. In order to verify the function of CmSGR genes in CHL degradation, CmSGR1 and CmSGR2 were transiently overexpressed and silenced using different plasmids in melon. Overexpression of CmSGR1 or CmSGR2 induced leaf yellowing or fruit ripening, while silencing of CmSGR1 or CmSGR2 via RNA interference delayed CHL breakdown during fruit ripening or leaf senescence compared with the wild type. Next, the expression profile was analyzed, and we found that CmSGR genes were expressed ubiquitously. Moreover, CmSGR1 and CmSGR2 were upregulated, and promoted fruit ripening. CmSGR3 and CmSGR4 were more highly expressed in leaves, cotyledon, and stem compared with CmSGR1 or CmSGR2. Thus, we conclude that CmSGR genes are crucial for fruit ripening and leaf senescence. CmSGR protein structure and function were further clarified to provide a theoretical foundation and valuable information for improved performance of melon.

Different color regulation mechanism in willow barks determined using integrated metabolomics and transcriptomics analyses

“…The higher expression of POR and CRD1 in the green bark may explain the maintenance of green pigmentation. Overexpression of the stay-green (SGR) protein in melon led to CHL degradation and leaf yellowing [ 50 ]. The highest expression of SGR (IMY05_005G0141100) was observed in the red bark, whereas another SGR (IMY05_016G0094700) was silenced in the green bark, causing green coloration.…”

Integrated Metabolomics and Transcriptomics Analyses Reveal Anthocyanin and Carotenoid Biosynthesis Involved in Color Development in Willow Bark

“…The higher expression of POR and CRD1 in the green bark may explain the reason for maintenance of green pigmentation. The stay-green (SGR) protein was overexpressed in melon affecting CHL degradation and leaf yellowing [47]. Among the three barks, the highest expression of SGR (IMY05_005G0141100) was observed in the red bark and other SGR (IMY05_016G0094700) was silenced in the green bark, causing the green coloration.…”

Genome-Wide Identification and Characterization of Tea SGR Family Members Reveal Their Potential Roles in Chlorophyll Degradation and Stress Tolerance

“…Armstead et al were the first to identify the gene governing Mendel's green cotyledon trait in Arabidopsis thaliana, Pisum sativum and Festuca pratensis [8], which is now called STAY-GREEN 1 (SGR1) or NONYELLOEING1 (NYE1). Subsequently, SGR homologs were widely identified in other plants, such as Oryza sativa [9], Solanum lycopersicum [10], Capsicum annuum [10], Medicago truncatula [11], Glycine max [12], Cucumis melo L. [13] and Citrus sinensis [14]. The SGR family is categorized into two subfamilies: the SGR and SGR-like (SGRL) subfamilies.…”

“…All SGR homologs are localized in chloroplasts and contain chloroplast transit peptides, conserved SGR domains and variable C-terminal regions [2,15]. The distinguishing feature between SGR and SGRL lies in the presence of a cysteine-rich motif (CRM, C-X3C-X-C2-F-P-X5-P), essential for Mg dechelatase activity and significant in Chl degradation, which is found in the C-terminus of most SGR proteins but absent in SGRL proteins [13,15].…”

“…SGRL contributes to Chl breakdown or turnover in pre-senescent leaves [5]. In the melon, the CmSGR1and CmSGR2-overexpressing lines exhibited fruit ripening and leaf yellowing, while the suppression of CmSGR1 and CmSGR2 delayed the degradation of Chl [13]. In the tomato, the inhibition of SlSGR1 in transgenic fruits elevated the accumulation of lycopene and β-carotene [19].…”