Impaired Magnesium Protoporphyrin IX Methyltransferase (ChlM) Impedes Chlorophyll Synthesis and Plant Growth in Rice

Abstract

Magnesium protoporphyrin IX methyltransferase (ChlM) catalyzes the formation of magnesium protoporphyrin IX monomethylester (MgPME) from magnesium protoporphyrin IX (MgP) in the chlorophyll synthesis pathway. However, no ChlM gene has yet been identified and studied in monocotyledonous plants. In this study, a spontaneous mutant, yellow-green leaf 18 (ygl18), was isolated from rice (Oryza sativa). This mutant showed yellow-green leaves, decreased chlorophyll level, and climate-dependent growth differences. Map-based cloning of this mutant identified the YGL18 gene LOC_Os06g04150. YGL18 is expressed in green tissues, especially in leaf organs, where it functions in chloroplasts. YGL18 showed an amino-acid sequence similarity to that of ChlM from different photosynthetic organisms. In vitro enzymatic assays demonstrated that YGL18 performed ChlM enzymatic activity, but ygl18 had nearly lost all ChlM activity. Correspondingly, the substrate MgP was largely accumulated while the product MgPME was reduced in ygl18 leaves. YGL18 is required for light-dependent and photoperiod-regulated chlorophyll synthesis. The retarded growth of ygl18 mutant plants was caused by the high light intensity. Moreover, the higher light intensity and longer exposure in high light intensity even made the ygl18 plants be more susceptible to death. Based on these results, it is suggested that YGL18 plays essential roles in light-related chlorophyll synthesis and light intensity–involved plant growth.

Metabolome and transcriptome analyses reveal chlorophyll and anthocyanin metabolism pathway associated with cucumber fruit skin color

“…The ChlH catalyzes protoporphyrin IX to form Mg-protoporphyrin IX. The magnesium protoporphyrin IX monomethyl ester formation was catalyzed magnesium protoporphyrin IX in chlorophyll synthesis pathway by ChlM [31]. The por is an important enzyme that catalyzes protochlorophyllide to generate chlorophyllide, and this step is a critical intermediate step in converting chlorophyll [32].…”

Integrated analyses of rice dark response and leaf color control reveal links with porphyrin and chlorophyll metabolism

“…OsYGL18 encodes a putative magnesium protoporphyrin IX methyltransferase (ChlM). When an OsYGL18 deletion mutant (ygl18) was transferred from dark to light, chlorophyll content increased and its expression was up-regulated (Wang et al, 2017c). OsZN encodes a thylakoid-bound protein of unknown function, and its mRNA level in constant light is higher than that in CD, indicating that OsZN transcription is controlled by light (Li et al, 2010).…”

“…OsWSP1 (Zhang et al, 2017b) OsGF14e (Manosalva et al, 2011) OspTAC2 (Wang et al, 2016a) OsYGL1 (Wu et al, 2007) OsGGR2 (Kimura et al, 2018) OsRAl (Zheng et al, 2019) OsYGL18 (Wang et al, 2017c) OsGIC (Kamau et al, 2015) OsRCCR1 (Tang et al, 2011) OsYGL8 (Zhu et al, 2016) OsGLK1 (Nakamura et al, 2009) OsREL2 (Yang et al, 2016a) OsYLD1 (Deng et al, 2017) OsGluRS (Liu et al, 2007) OsRLIN1 (Sun et al, 2011) OsYS83 (Chen et al, 2016a) OsGRA(t) (Chen et al, 2007) OsRLS1 (Jiao et al, 2012) OsYSA (Su et al, 2012) OsGRA78 (Wang et al, 2019) OsRNRS1 (Chen et al, 2015) OsYSL13 (Zhang et al, 2018a) OsGRY79 (Wan et al, 2015) OsRopGEF1 0 (Yoo et al, 2011) OsYSL16 (Zheng et al, 2012) OsHAD1 OsS6K (Sun et al, 2016) OsYSS1 (Zhou et al, 2017) OsHAP3A (Miyoshi et al, 2003) OsSGL1 (Hitoshi et al, 2012) OsZ2 (Han et al, 2012) OsHO1 OsSGR (Jiang et al, 2007) OsZ3 (Kim et al, 2018) OsHO2 (Li et al, 2014) OsSGRL (Rong et al, 2013) OsZN (Li et al, 2010) Detailed information is listed in additional file: Table S6. Rich factors for DEG-enriched metabolic pathways identified by KEGG analysis of darktreated rice.…”

“…proportion of chlorophyll contents and produced leaf color variation. In rice, dozens of genes identified as Chl biosynthesis enzymes have been cloned, including OsYGL18 (Wang et al, 2017c), OsChlH, OsChlD and OsChlI (Zhang et al, 2006a;Inagaki et al, 2015), OsPORA and OsPORB (Sakuraba et al, 2013), OsYGL1 (Wu et al, 2007), OsIspF (Huang et al, 2017), OsDVR (Wang et al, 2010), OsCAO1 and OsCAO2 (Lee et al, 2005;Yang et al, 2016b), OsCRD1 (Wang et al, 2017b), OsGluRS (Liu et al, 2007), OsIspE (Chen et al, 2018), OsV5B (Liu et al, 2016b) and OsMTS1 (Hong et al, 2018). Several genes associated with chlorophyll degradation, like OsNOL (Kusaba et al, 2007),…”

Integrated analyses of rice dark response and leaf color regulation reveal links with porphyrin and chlorophyll metabolism

“…Every chlorophyll metabolic pathway gene mutation that has led to the inactivation or deletion of its encoded enzyme has changed the proportion of chlorophyll contents and produced leaf color variation. In rice, dozens of genes identi ed as chlorophyll biosynthesis enzymes have been cloned, including OsYGL18 (Wang et al, 2017c), OsChlH, OsChlD and OsChlI (Zhang et al, 2006a;Inagaki et al, 2015), OsPORA and OsPORB (Sakuraba et al, 2013), OsYGL1 (Wu et al, 2007), OsIspF (Huang et al, 2017), OsDVR (Wang et al, 2010), OsCAO1 and OsCAO2 (Lee et al, 2005;Yang et al, 2016b), OsCRD1 (Wang et al, 2017b), OsGluRS (Liu et al, 2007), OsIspE (Chen et al, 2018), OsV5B (Liu et al, 2016b) and OsMTS1 (Hong et al, 2018). Several genes associated with chlorophyll degradation, like OsNOL (Kusaba et al, 2007), OsNYC3 (Morita et al, 2009) and OsSGRL (Rong et al, 2013), have also been cloned.…”