Transcriptome Changes Induced by Different Potassium Levels in Banana Roots

Abstract

Potassium plays an important role in enhancing plant resistance to biological and abiotic stresses and improving fruit quality. To study the effect of potassium nutrient levels on banana root growth and its regulation mechanism, four potassium concentrations were designed to treat banana roots from no potassium to high potassium. The results indicated that K2 (3 mmol/L K₂SO₄) treatment was a relatively normal potassium concentration for the growth of banana root, and too high or too low potassium concentration was not conducive to the growth of banana root. By comparing the transcriptome data in each treatment in pairs, 4454 differentially expressed genes were obtained. There were obvious differences in gene function enrichment in root systems treated with different concentrations of potassium. Six significant expression profiles (profile 0, 1, 2, 7, 9 and 13) were identified by STEM analysis. The hub genes were FKF1, HsP70-1, NRT1/PTR5, CRY1, and ZIP11 in the profile 0; CYP51 in profile 1; SOS1 in profile 7; THA, LKR/SDH, MCC, C4H, CHI, F3'H, 2 PR1s, BSP, TLP, ICS, RO, chitinase and peroxidase in profile 9. Our results provide a comprehensive and systematic analysis of the gene regulation network in banana roots under different potassium stress.

Keywords: banana; potassium; root; transcriptome.

Figure 1

Effects of different concentration of potassium stress on the growth of banana roots. K0: 0 mmol/L K₂SO₄ treated banana root; K1: 0.03 mmol/L K₂SO₄ treated banana root; K2: 3 mmol/L K₂SO₄ treated banana root; K3: 200 mmol/L K₂SO₄ treated banana root.

Figure 2

Transcript abundance measurements at each potassium concentration treatment. (A) The frequency represents the number of genes per category according to FPKM expression value. The number of total considered expressed genes (FPKM ≥ 2) for each moment is presented in brackets. (B) Venn diagram of expressed genes (FPKM ≥ 2) for each library (K0: 22,738 genes; K1: 22,383 genes; K2: 21,438 genes; K3: 21,752 genes). The number of common expressed genes in each intersection area is presented.

Figure 3

Upset Venn illustrating the number of DEGs between different concentration potassium treated banana roots. The horizontal orange bar graph on the left side represents the element statistics of each set, the single black point in the middle matrix represents the element unique to a set, the line between points and points represents the intersection unique to different sets, and the vertical blue bar graph represents the corresponding intersection element values.

Figure 4

GO molecular function analysis of DEGs detected in banana roots in response to different concentration of potassium. The ratio was the proportion of the number of DEGs in the total number of genes in each GO term. K1 up-regulated: The GO terms significantly enriched in K1 up-regulated DEGs. K1 down-regulated: The GO terms significantly enriched in K1 down-regulated DEGs. K2 up-regulated: The GO terms significantly enriched in K2 up-regulated DEGs. K2 down-regulated: The GO terms significantly enriched in K2 down-regulated DEGs. K3 up-regulated: The GO terms significantly enriched in K3 up-regulated DEGs. K3 down-regulated: The GO terms significantly enriched in K3 down-regulated DEGs.

Figure 4

GO molecular function analysis of DEGs detected in banana roots in response to different concentration of potassium. The ratio was the proportion of the number of DEGs in the total number of genes in each GO term. K1 up-regulated: The GO terms significantly enriched in K1 up-regulated DEGs. K1 down-regulated: The GO terms significantly enriched in K1 down-regulated DEGs. K2 up-regulated: The GO terms significantly enriched in K2 up-regulated DEGs. K2 down-regulated: The GO terms significantly enriched in K2 down-regulated DEGs. K3 up-regulated: The GO terms significantly enriched in K3 up-regulated DEGs. K3 down-regulated: The GO terms significantly enriched in K3 down-regulated DEGs.

Figure 4

GO molecular function analysis of DEGs detected in banana roots in response to different concentration of potassium. The ratio was the proportion of the number of DEGs in the total number of genes in each GO term. K1 up-regulated: The GO terms significantly enriched in K1 up-regulated DEGs. K1 down-regulated: The GO terms significantly enriched in K1 down-regulated DEGs. K2 up-regulated: The GO terms significantly enriched in K2 up-regulated DEGs. K2 down-regulated: The GO terms significantly enriched in K2 down-regulated DEGs. K3 up-regulated: The GO terms significantly enriched in K3 up-regulated DEGs. K3 down-regulated: The GO terms significantly enriched in K3 down-regulated DEGs.

Figure 5

Short time-series expression miner (STEM) clustering on DEGs with the increase of potassium concentration. (A), all 20 profiles, with the colored profiles were significant (p < 0.05). (B), six significant gene expression profiles, with the number of genes and the p-value were shown.

Figure 5

Short time-series expression miner (STEM) clustering on DEGs with the increase of potassium concentration. (A), all 20 profiles, with the colored profiles were significant (p < 0.05). (B), six significant gene expression profiles, with the number of genes and the p-value were shown.

Figure 6

Interaction network of DEGs in profile 0, 1, 7 and 9. The hub genes were represented in the largest font. (A) Interaction network of DEGs in profile 0. (B) Interaction network of DEGs in profile 1. (C) Interaction network of DEGs in profile 7. (D) Interaction network of DEGs in profile 9.

Figure 7

Relative gene expression of 8 randomly selected genes. The blue lines represent the relative intensity of real-time quantitative RT-PCR. The experiments were repeated three times. The error bars represent ± SE. n = 3.