Transcriptional and Metabolic Responses of Maize Shoots to Long-Term Potassium Deficiency

Abstract

Potassium is important for plant growth and crop yield. However, the effects of potassium (K⁺) deficiency on silage maize biomass yield and how maize shoot feedback mechanisms of K⁺ deficiency regulate whole plant growth remains largely unknown. Here, the study aims to explore the maize growth, transcriptional and metabolic responses of shoots to long-term potassium deficiency. Under the K⁺ insufficiency condition, the biomass yield of silage maize decreased. The transcriptome data showed that there were 922 and 1,107 differential expression genes in DH605 and Z58, respectively. In the two varieties, 390 differently expressed overlapping genes were similarly regulated. These genes were considered the fundamental responses to K⁺ deficiency in maize shoots. Many stress-induced genes are involved in transport, primary and secondary metabolism, regulation, and other processes, which are involved in K⁺ acquisition and homeostasis. Metabolic profiles indicated that most amino acids, phenolic acids, organic acids, and alkaloids were accumulated in shoots under K⁺ deficiency conditions and part of the sugars and sugar alcohols also increased. It revealed that putrescine and putrescine derivatives were specifically accumulated under the K⁺ deficiency condition, which may play a role in the feedback regulation of shoot growth. These results confirmed the importance of K⁺ on silage maize production and provided a deeper insight into the responses to K⁺ deficiency in maize shoots.

Keywords: biomass yield; metabolome; potassium; silage maize; transcriptome.

Figure 1

Effect of K⁺ deficiency on maize growth. (A,B) Showed phenotypes of maize DH605 and Z58 under K⁺ treatment for 12 days, respectively. (C–E) showed the variations of average stem diameter, plant height, and plant fresh weight under K⁺ deficiency condition for 12 days, respectively. Two maize varieties, DH605 and Z58, were analyzed to K⁺ deficiency, respectively. CK and LK represent K⁺ sufficiency (4 mM) and K⁺ deficiency (0.1 mM). Scale bars in (A,B) represent 10 cm. The experiments were repeated three times. ^* and ^** on histograms mean the significant difference at the p≤0.05 and p≤0.01 level, respectively. Bars mean SD.

Figure 2

Shoot potassium content (A), differential expression genes (B), leaf net photosynthetic rate (C), and stomatal conductance (D) of maize DH605 and Z58 under K⁺ deficiency treatment. CK and LK represent K⁺ sufficiency (4 mM) and K⁺ deficiency (0.1 mM), respectively. The experiments were repeated three times. ^** on histograms mean the significant difference at the p ≤ 0.05 and p ≤ 0.01 level, respectively. Bars mean SD.

Figure 3

KEGG pathway analysis of DEGs under K⁺ deficiency treatment in DH605 and Z58. (A) KEGG pathway enrichment of DEGs under K⁺ deficiency treatment in DH605. (B) KEGG pathway enrichment of DEGs under K⁺ deficiency treatment in Z58. (C) The top-level pathways of DEGs under K⁺ deficiency treatment in DH605 and Z58 (p ≤ 0.05).

Figure 4

KEGG analysis of DAMs and DEGs under K⁺ deficiency treatment in DH605 (A) and Z58 (B) (p ≤ 0.05).

Figure 5

The metabolites that varied significantly in DH605 and Z58 after exposure to K⁺ deficiency. The first and second box of each metabolite indicates the varied metabolites of DH605 and Z58 after exposure to K⁺ deficiency, respectively. The first and second triangle of each gene indicates the varied genes of DH605 and Z58 after exposure to K⁺ deficiency, respectively.