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Background: Both photosynthetic pigments and chloroplasts in plant leaf cells play an important role in deciding on the photosynthetic capacity and efficiency in plants. Systematical investigating the regulatory mechanism of chloroplast development and chlorophyll (Chl) content variation is necessary for clarifying the photosynthesis mechanism for crops., Objective: This study aims to explore the critical regulatory mechanism of leaf color mutation in a yellow-green leaf sesame mutant Siyl-1., Methods: We performed the genetic analysis of the yellow-green leaf color mutation using the F 2 population of the mutant Siyl-1. We compared the morphological structure of the chloroplasts, chlorophyll content of the three genotypes of the mutant F 2 progeny. We performed the two-dimensional gel electrophoresis (2-DE) and compared the protein expression variation between the mutant progeny and the wild type., Results: Genetic analysis indicated that there were 3 phenotypes of the F 2 population of the mutant Siyl-1, i.e., YY type with light-yellow leaf color (lethal); Yy type with yellow-green leaf color, and yy type with normal green leaf color. The yellow-green mutation was controlled by an incompletely dominant nuclear gene, Siyl-1. Compared with the wild genotype, the chloroplast number and the morphological structure in YY and Yy mutant lines varied evidently. The chlorophyll content also significantly decreased (P < 0.05). The 2-DE comparison showed that there were 98 differentially expressed proteins (DEPs) among YY, Yy, and yy lines. All the 98 DEPs were classified into 5 functional groups. Of which 82.7% DEPs proteins belonged to the photosynthesis and energy metabolism group., Conclusion: The results revealed the genetic character of yellow-green leaf color mutant Siyl-1. 98 DEPs were found in YY and Yy mutant compared with the wild genotype. The regulation pathway related with the yellow leaf trait mutation in sesame was analyzed for the first time. The findings supplied the basic theoretical and gene basis for leaf color and chloroplast development mechanism in sesame.

Birch (Betula platyphylla × B. pendula) is an important tree for landscaping due to its attractive white bark and straight trunk. In this study, we characterized a T-DNA yellow-green leaf mutant, yl. We identified six insertion sites (ISs) in the mutant by genome resequencing and found a 40-kb deletion containing BpGLK1 around IS2 on chromosome 2. Complementation experiments with the yl mutant and repression of BpGLK1 in wild-type plants confirmed that BpGLK1 was responsible for the mutated phenotype. Physiological and ultrastructural analyses showed that the leaves of the yl mutant and BpGLK1-repression lines had decreased chlorophyll content and defective chloroplast development compared to the wild-type. Furthermore, the loss function of BpGLK1 also affected photosynthesis in leaves. Transcriptomics, proteomics, and ChIP-PCR analysis revealed that BpGLK1 directly interacted with the promoter of genes related to antenna proteins, chlorophyll biosynthesis, and photosystem subunit synthesis, and regulated their expression. Overall, our research not only provides new insights into the mechanism of chloroplast development and chlorophyll biosynthesis regulated by BpGLK1, but also provides new transgenic birch varieties with various levels of yellowing leaves by repressing BpGLK1 expression., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Key Message: We identified IspF gene through yellow-green leaf mutant 505ys in rice. OsIspF was expressed in all tissues detected, and its encoded protein was targeted to the chloroplast. On expression levels of genes in this mutant, OsIspF itself and the genes encoding other enzymes of the MEP pathway and chlorophyll synthase were all up-regulated, however, among eight genes associated with photosynthesis, only psaA, psaN and psbA genes for three reaction center subunits of photosystem obviously changed. Isoprenoids are the most abundant natural compounds in all organisms, which originate from the basic five-carbon units isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). In plants, IPP and DMAPP are synthesized through two independent pathways, the mevalonic acid pathway in cytoplasm and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway in plastids. The MEP pathway comprises seven enzymatic steps, in which IspF is the fifth enzyme. So far, no IspF gene has been identified in monocotyledonous plants. In this study, we isolated a leaf-color mutant, 505ys, in rice (Oryza sativa). The mutant displayed yellow-green leaf phenotype, reduced level of photosynthetic pigments, and arrested development of chloroplasts. By map-based cloning of this mutant, we identified OsIspF gene (LOC&#95;Os02g45660) showing significant similarity to IspF gene of Arabidopsis, in which a missense mutation occurred in the mutant, resulting in an amino acid change in the encoded protein. OsIspF gene was expressed in all tissues detected, and its encoded protein was targeted to the chloroplast. Further, the mutant phenotype of 505ys was complemented by transformation with the wild-type OsIspF gene. Therefore, we successfully identified an IspF gene in monocotyledonous plants. In addition, real-time quantitative RT-PCR implied that a positive regulation could exist between the OsIspF gene and the genes encoding other enzymes of the MEP pathway and chlorophyll synthase. At the same time, it also implied that the individual genes involved in the MEP pathway might differentially regulated expression levels of the genes associated with photosynthesis.

Ferredoxins (Fds) are small iron-sulfur proteins that mediate electron transfer in a wide range of metabolic reactions. Besides Fds, there is a type of Fd-like proteins designated as FdC, which have conserved elements of Fds, but contain a significant C-terminal extension. So far, only two FdC genes of Arabidopsis (Arabidopsis thaliana) have been identified in higher plants and thus the functions of FdC proteins remain largely unknown. In this study, we isolated a yellow-green leaf mutant, 501ys, in rice (Oryza sativa). The mutant exhibited yellow-green leaf phenotype and reduced chlorophyll level. The phenotype of 501ys was caused by mutation of a gene on rice chromosome 3. Map-based cloning of this mutant resulted in identification of OsFdC2 gene (LOC&#95;Os03g48040) showing high identity with Arabidopsis FdC2 gene (AT1G32550). OsFdC2 was expressed most abundantly in leaves and its encoded protein was targeted to the chloroplast. In 501ys mutant, a missense mutation was detected in DNA sequence of the gene, resulting in an amino acid change in the encoded protein. The mutant phenotype was rescued by introduction of the wild-type gene. Therefore, we successfully identified FdC2 gene via map-based cloning approach, and demonstrated that mutation of this gene caused yellow-green leaf phenotype in rice., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)