Figure 1.
Growth and ion content analysis of rice seedlings during potassium nutrient deficiency.
(A) Analysis was performed 5 days after transfer of seedling in KP and KM medium. Phenotypes of rice seedlings under normal, K+ deficient and resupply conditions (KP, KM and KR). (B) Length of rice shoot, root and leaf blade under three different conditions. (C) Fresh and dry weight comparison of rice seedling. (D) K+ and Na+ content of rice seedlings. Differences between mean values of treatments and controls were compared using t - tests (* P<0.05, ** P<0.01).
Figure 2.
Overview of the changes in transcripts in potassium sufficient, deficient and resupply condition.
(A) Principal component analysis (PCA) of the changes in transcript abundance in rice seedling under different condition. (B) Venn diagram showing the number of differentially expressed genes (P<0.05 and fold change equal or more than 2) in response to KM/KP and KR/KM in seedling.
Table 1.
Correlation data from microarray analysis.
Figure 3.
Hierarchical cluster analysis.
(A) Hierarchical cluster analysis of the 722 potassium responsive genes found in potassium deficient condition, (B) 1876 genes found in potassium resupply condition and (C) 307 genes found common between potassium deficient and resupply condition, which were truly differentially expressing under K+ deficient conditions based on their reversal of expression upon resupply condition.
Figure 4.
Confirmation of microarray data for selected genes by qRT-PCR analysis.
Nineteen genes were selected and their expression profiles were assessed by qRT-PCR in all three conditions to verify the microarray data by using three biological replicates. Y-axis represents relative expression values obtained after normalizing the data against maximum expression value and X-axis shows different nutritional treatments. Blue bars represent the expression from microarrays, while red bars represent the qRT- PCR values.
Figure 5.
Functional categorization of potassium responsive genes into different categories.
Detailed classification of genes showing transcriptional changes in the several categories based on the gene ontology (GO) and their putative function.
Table 2.
Different category of differentially regulated genes in potassium deficient condition.
Figure 6.
K-means cluster analysis of differentially expressed genes.
All the genes categorized into 20 clusters and again grouped together to make 7 groups, based on their similar expression patterns but different expression amplitudes. The normalized log transformed signal values were plotted for all the conditions. The number of genes in the clusters is indicated upper side of the heatmap.
Table 3.
Differentially expressed genes from present microarray data and data obtained from 2 week K+-starved Arabidopsis shoot-root (Armengaud et al. 2004), roots of rice plants after 6 h, 3 days and 5 days (Ma et al. 2012).
Figure 7.
Model of plant responses and adaptation to potassium deficiency.
Under low K+ conditions a large number of genes are affected. This condition alters plant metabolic as well as signaling responses. During K+ deprivation conditons, the initial reaction of plant is to sense the K+ deficiency followed by activation of several genes and gene networks, which might be working in tandem. As depected several genes encoding metabolic enzymes, protein involved in stress signaling, transporters, transcription factors could be the final target to bring about a physiological response such as tolerance or adaptation to low-K+ condition. Putative factors of K+ deficiency and adaptive responses are shown in boxes. Genes of related components are written below the boxes.