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. 2022 Jul 28:13:952877.
doi: 10.3389/fpls.2022.952877. eCollection 2022.

Genome-wide characterization and analysis of Golden 2-Like transcription factors related to leaf chlorophyll synthesis in diploid and triploid Eucalyptus urophylla

Zhao Liu  1   2   3 , Tao Xiong  4 , Yingwei Zhao  4 , Bingfa Qiu  4 , Hao Chen  1   2   3 , Xiangyang Kang  1   2   3 , Jun Yang  1   2   3
Affiliations

Genome-wide characterization and analysis of Golden 2-Like transcription factors related to leaf chlorophyll synthesis in diploid and triploid Eucalyptus urophylla

Zhao Liu et al. Front Plant Sci. .

Abstract

Golden 2-Like (GLK) transcription factors play a crucial role in chloroplast development and chlorophyll synthesis in many plant taxa. To date, no systematic analysis of GLK transcription factors in tree species has been conducted. In this study, 40 EgrGLK genes in the Eucalyptus grandis genome were identified and divided into seven groups based on the gene structure and motif composition. The EgrGLK genes were mapped to 11 chromosomes and the distribution of genes on chromosome was uneven. Phylogenetic analysis of GLK proteins between E. grandis and other species provided information for the high evolutionary conservation of GLK genes among different species. Prediction of cis-regulatory elements indicated that the EgrGLK genes were involved in development, light response, and hormone response. Based on the finding that the content of chlorophyll in mature leaves was the highest, and leaf chlorophyll content of triploid Eucalyptus urophylla was higher than that of the diploid control, EgrGLK expression pattern in leaves of triploid and diploid E. urophylla was examined by means of transcriptome analysis. Differential expression of EgrGLK genes in leaves of E. urophylla of different ploidies was consistent with the trend in chlorophyll content. To further explore the relationship between EgrGLK expression and chlorophyll synthesis, co-expression networks were generated, which indicated that EgrGLK genes may have a positive regulatory relationship with chlorophyll synthesis. In addition, three EgrGLK genes that may play an important role in chlorophyll synthesis were identified in the co-expression networks. And the prediction of miRNAs targeting EgrGLK genes showed that miRNAs might play an important role in the regulation of EgrGLK gene expression. This research provides valuable information for further functional characterization of GLK genes in Eucalyptus.

Keywords: EgrGLK; chlorophyll synthesis; co-expression networks; miRNA; polyploid; transcriptome analysis.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Chromosomal location of EgrGLK genes in Eucalyptus grandis. Genes of the same color represents a pair of segmented duplicated genes, and genes of different colors represent different gene pairs. No segmental duplication in black genes.
Figure 2
Figure 2
Synteny analysis of GLK genes in different plants. Synteny analyses of GLK genes between E. grandis and maize (A), tomato (B), and Arabidopsis (C). Red lines indicate the homologous GLK genes between E. grandis genome and other plant genomes.
Figure 3
Figure 3
Phylogenetic analysis of GLK proteins from E. grandis, maize, Arabidopsis, and tomato. Different GLK protein groups are indicated by different colors. The star, triangle, circle, and square represent E. grandis, maize, Arabidopsis, and tomato GLK proteins, respectively.
Figure 4
Figure 4
Phylogenetic tree, conserved motifs, and gene structure of EgrGLK genes of E. grandis. (A) Phylogenetic reconstruction for EgrGLK proteins. (B) Ten conserved motifs indicated by different colors. (C) Gene structure with exons and introns indicated.
Figure 5
Figure 5
Analysis of cis-acting regulatory element in promoter regions of EgrGLK genes of E. grandis. Numerals in different color boxes indicate the number of the main cis-elements of EgrGLK genes. Cis-elements of different responsive types are indicated by different colors.
Figure 6
Figure 6
Measurement of chlorophyll content in leaves of E. urophylla. Phenotype (A) and chlorophyll content (B) of young leaves (YL), mature leaves (ML), and senescent leaves (SL) of diploid (2X) and triploid (3X) clones.
Figure 7
Figure 7
Expressions patterns of EgrGLK genes in leaves of E. urophylla. The expression patterns of EgrGLK genes in the terminal bud (TB), young leaves (YL), mature leaves (ML), and senescent leaves (SL) of diploid (A) and triploid (B) clones.
Figure 8
Figure 8
Differential expression of EgrGLK genes in the terminal bud (TB), young leaves (YL), mature leaves (ML), and senescent leaves (SL) of diploid and triploid clones. Circles represent highly expressed genes common to the diploid and triploid clones, and squares represent genes highly expressed only in the triploid clone.
Figure 9
Figure 9
Co-expression network of EgrGLK genes and chlorophyll synthesis related genes. Positive correlation network (A) and negative correlation network (B) between EgrGLK genes and chlorophyll synthesis related genes. Circles represent EgrGLK genes, squares represent chlorophyll synthesis related genes, and the size of the circle or square represents the number of relationships between genes.
Figure 10
Figure 10
Regulatory networks were divided into (A-E) according to the number of targeting relationship between miRNAs and EgrGLK genes.
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