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. 2021 Oct 22;10(11):2261.
doi: 10.3390/plants10112261.

Light Deficiency Inhibits Growth by Affecting Photosynthesis Efficiency as well as JA and Ethylene Signaling in Endangered Plant Magnolia sinostellata

Danying Lu  1   2 , Bin Liu  3 , Mingjie Ren  1   2 , Chao Wu  1   2 , Jingjing Ma  1   2 , Yamei Shen  1   2
Affiliations

Light Deficiency Inhibits Growth by Affecting Photosynthesis Efficiency as well as JA and Ethylene Signaling in Endangered Plant Magnolia sinostellata

Danying Lu et al. Plants (Basel). .

Abstract

The endangered plant Magnolia sinostellata largely grows in the understory of forest and suffers light deficiency stress. It is generally recognized that the interaction between plant development and growth environment is intricate; however, the underlying molecular regulatory pathways by which light deficiency induced growth inhibition remain obscure. To understand the physiological and molecular mechanisms of plant response to shading caused light deficiency, we performed photosynthesis efficiency analysis and comparative transcriptome analysis in M. sinostellata leaves, which were subjected to shading treatments of different durations. Most of the parameters relevant to the photosynthesis systems were altered as the result of light deficiency treatment, which was also confirmed by the transcriptome analysis. Gene Ontology and KEGG pathway enrichment analyses illustrated that most of differential expression genes (DEGs) were enriched in photosynthesis-related pathways. Light deficiency may have accelerated leaf abscission by impacting the photosynthesis efficiency and hormone signaling. Further, shading could repress the expression of stress responsive transcription factors and R-genes, which confer disease resistance. This study provides valuable insight into light deficiency-induced molecular regulatory pathways in M. sinostellata and offers a theoretical basis for conservation and cultivation improvements of Magnolia and other endangered woody plants.

Keywords: Magnolia sinostellata; RNA-seq; endangered species; gene regulation; light deficiency.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Phenotypic and physiological changes of M. sinostellata seedlings under light deficiency. (A) Phenotypic shifting of M. sinostellata during experiment. (B) Net photosynthesis rate, Pn. (C) Intercellular CO2 concentration, Ci. (D) Stomatal conductance, Gs. (E) Transpiration rate, Tr. (F) Light use efficiency, LUE. (G) Water use efficiency, WUE. (H) Rubiso activity. (I) Maximum Chl fluorescence yield obtained with dark-adapted leaf, Fm. (J) Minimum Chl fluorescence yield obtained with dark-adapted leaf, Fo. (K) Maximal photochemical efficiency, Fv/Fm. (L) Excitation energy capture efficiency of PSII, Fv’/Fm’. (M) Activity of PSII reaction centers, Fv/Fo. (N) Non-photochemical quenching, NPQ. (O) Photochemical quenching, qP. (P) Yield of PSII photochemistry, ΦPSII.
Figure 2
Figure 2
Analysis of DEGs involved in photosynthesis related pathways in M. sinostellata. (A) GO enrichment analysis of 22,433 DEGs. (B) KEGG enrichment analysis of 22,433 DEGs. The top 20 GO and KEGG Terms with the smallest Qvalue were selected to plot the chart, respectively. (C) Volcano plots of DEGs involved in antenna protein. (D) Trends of DEGs related to antenna protein. (E) Volcano plots of DEGs involved in photosynthesis. (F) Trends of DEGs related to photosynthesis. (G) Volcano plots of DEGs involved in carbon fixation. (H) Trends of DEGs related to carbon fixation.
Figure 3
Figure 3
Heatmaps of DEGs involved in photosynthesis-related pathways in M. sinostellata. (A) Heatmaps of the expression patterns of genes involved in ‘photosynthesis-antenna protein’ pathway under light deficiency and normal light conditions. (B) Heatmaps of the expression patterns of DEGs participated in ‘photosynthesis’ pathway under light deficiency and normal light conditions. (C) Heatmaps of the expression patterns of DEGs related to ‘carbon fixation in photosynthetic organisms’ pathway under light deficiency and normal light conditions.
Figure 4
Figure 4
The impact of light deficiency on plant hormone concentration and signaling pathways. (A) Heatmap of genes involved in ethylene signal transduction under light deficiency and normal light conditions. (B) Heatmaps of genes involved in jasmonic acid signaling under light deficiency and normal light conditions. (C) Concentrations of ethylene at d0 and d15 under light deficiency and normal light conditions. (D) Concentrations of jasmonic acid at d0 and d15 under light deficiency and normal light conditions. (E) qRT-PCR analysis of key genes involved in plant hormone signaling under light deficiency and control conditions for 0 d, 5 d, and 15 d. Data are the means of three biological replicates and three technical replicates. The 2−ΔΔct method was employed to conduct the gene differential expression analysis. * indicates significant differences in comparison with the control groups corresponding to time points at p < 0.05.
Figure 5
Figure 5
Analysis of TIFY family genes, mTERF family genes, and R-genes in M. sinostellata. (A) The expression profile of MsTIFY gene family in leaves of M. sinostellata under light deficiency and untreated conditions. Two pairs of duplicated paralogs are marked by lowercase letters. (B) Phylogenetic tree of TIFY protein sequences from M. sinostellata, Arabidopsis thaliana and Populus trichocarpa, which was constructed using the NJ (neighbor-joining) method with 1000 bootstrap replications. (C) Expression profiles of MsmTERFs under light deficiency and normal light conditions. (D) Phylogenetic tree of mTERF protein sequences from M. sinostellata, Arabidopsis thaliana, and Zea mays, which was constructed using the NJ method with 1000 bootstrap replications. (E) Expression patterns of 13 classification of R-genes in M. sinostellata under light deficiency and normal light conditions.
Figure 6
Figure 6
Hypothetical model of the light deficiency response mechanism in the endangered species M. sinostellata.
See this image and copyright information in PMC

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