StABI5 Involved in the Regulation of Chloroplast Development and Photosynthesis in Potato

Abstract

Abscisic acid (ABA) insensitive 5 (ABI5)-a core transcription factor of the ABA signaling pathway-is a basic leucine zipper transcription factor that plays a key role in the regulation of seed germination and early seedling growth. ABI5 interacts with other phytohormone signals to regulate plant growth and development, and stress responses in Arabidopsis, but little is known about the functions of ABI5 in potatoes. Here, we find that StABI5 is involved in the regulation of chloroplast development and photosynthesis. Genetic analysis indicates that StABI5 overexpression transgenic potato lines accelerate dark-induced leaf yellowing and senescence. The chlorophyll contents of overexpressed StABI5 transgenic potato lines were significantly decreased in comparison to those of wild-type Desiree potatoes under dark conditions. Additionally, the RNA-sequencing (RNA-seq) analysis shows that many metabolic processes are changed in overexpressed StABI5 transgenic potatoes. Most of the genes involved in photosynthesis and carbon fixation are significantly down-regulated, especially the chlorophyll a-b binding protein, photosystem I, and photosystem II. These observations indicate that StABI5 negatively regulates chloroplast development and photosynthesis, and provides some insights into the functions of StABI5 in regard to potato growth.

Keywords: StABI5; chlorophyll; chloroplast development; photosynthesis; potato.

Figure 1

AtABI5 regulates chlorophyll catabolism in Arabidopsis. (A) Phenotype of the abi5-1 mutant and overexpressed AtABI5 (OE) transgenic Arabidopsis leaves after 0, 5, and 8 days of dark treatment, respectively. (B) Phenotype and chlorophyll content of the abi5-1 mutant and overexpressed AtABI5 (OE) transgenic lines after 0 and 8 days of dark treatment, respectively. The data represent the mean ± SD of 3 independent experiments. Asterisks denote Student’s t-test significant differences as compared with Col (** P < 0.01). (C) Transcription levels of chlorophyll catabolism-related genes in Arabidopsis after dark treatment. The data represents the mean ± SD of 3 independent experiments.

Figure 2

Identification and subcellular localization of StABI5 transgenic potatoes. (A) Identification of StABI5 transgenic potato lines by leaf PCR. The amplified PCR product was 1547 bp when using primers P35S F and StABI5 R. De: Desiree. (B) Western blot analysis of StABI5 protein expression in StABI5 transgenic potato lines. (C) The transcription level of StABI5 in StABI5 transgenic potato lines obtained by qRT-PCR. StACTIN58 was used as an internal control. (D) Subcellular localization of StABI5 in tobacco (Nicotiana tabacum). Tobacco transiently expressed Agrobacterium strain containing the PStABI5::StABI5-GFP vector, and the localization of GFP was observed by laser confocal microscopy. Bars, 50 μm.

Figure 3

StABI5 regulates chlorophyll catabolism under dark conditions in potato. (A) Overexpressed StABI5 (StABI5-OE) transgenic potato leaves accelerate yellowing and senescence under dark conditions. (B) Chlorophyll contents of StABI5-OE transgenic potato and Desiree leaves under dark conditions. The data represent an average of five leaves with three duplicates. Error bars indicate ±SD for triplicates. Asterisks denote Student’s t-test significant differences as compared with Desiree potatoes (* P <0.05; ** P < 0.01). (C) Transcription levels of chlorophyll metabolism-related genes PGSC0003DMG400012666 (StRBCS_2C), PGSC0003DMG400013416 (StCAB3C), PGSC0003DMG400002261 (StCV) and PGSC0003DMG400030219 (StNYC1) in StABI5-OE transgenic potato lines and Desiree leaves when treated with continuous darkness for 0, 2 and 4 days.

Figure 4

Analysis of differentially expressed genes. (A) Proportions of clean reads that were unmapped, mapped to multiple genes, and mapped to unique genes, which were plotted by three replicates of De, StABI5, De_2DK, and StABI5_2DK, respectively. (B) Statistical analysis of differentially expressed genes between different samples. (C) Analysis of the overlap of differentially expressed genes between different comparison combinations by Venn diagram. (D) Cluster analysis of differentially expressed genes by heat map. Red represents high gene abundance, blue represents low gene abundance.

Figure 5

Gene ontology (GO) and KEGG pathway enrichment analysis of differentially expressed genes (DEGs). (A) The top 30 most enriched GO terms found in the analysis of DEGs in StABI5 vs. De group. Different colors represent molecular functions (MF), cellular components (CC), and biological processes (BP). Gene ontologies were ranked by their significance. (B) The top 30 most enriched GO terms found in the analysis of DEGs in StABI5_2DK vs. De_2Dk group. (C) The top 20 functionally enriched KEGG pathways found in the analysis of DEGs in StABI5 vs. De group. (D) The top 20 functionally enriched KEGG pathways found in the analysis of DEGs in StABI5_2DK vs. De_2Dk group.

Figure 6

StABI5 involved in plant hormone signal transduction in potato. DEGs of plant hormone signals transduction were marked in StABI5 vs. De group. Green boxes represent down-regulated genes, red boxes indicate up-regulated genes, and yellow boxes represent both up- and down-regulated genes.