Dissecting the Regulatory Network of Leaf Premature Senescence in Maize (Zea mays L.) Using Transcriptome Analysis of ZmELS5 Mutant

Abstract

Leaf premature senescence largely determines maize (Zea mays L.) grain yield and quality. A natural recessive premature-senescence mutant was selected from the breeding population, and near-isogenic lines were constructed using Jing24 as the recurrent parent. In the near-isogenic lines, the dominant homozygous material was wild-type (WT), and the recessive material of early leaf senescence was the premature-senescence-type ZmELS5. To identify major genes and regulatory mechanisms involved in leaf senescence, a transcriptome analysis of the ZmELS5 and WT near-isogenic lines (NILs) was performed. A total of 8,796 differentially expressed transcripts were identified between ZmELS5 and WT, including 3,811 up-regulated and 4,985 down-regulated transcripts. By combining gene ontology, Kyoto Encyclopedia of Genes and Genomes, gene set, and transcription factor enrichment analyses, key differentially expressed genes were screened. The senescence regulatory network was predicted based on these key differentially expressed genes, which indicated that the senescence process is mainly regulated by bHLH, WRKY, and AP2/EREBP family transcription factors, leading to the accumulations of jasmonic acid and ethylene. This causes stress responses and reductions in the chlorophyll a/b-binding protein activity level. Then, decreased ATP synthase activity leads to increased photosystem II photodamage, ultimately leading to leaf senescence.

Keywords: leaf premature senescence; maize (Zea mays L.); regulatory networks; transcriptome analysis.

Figure 1

Phenotyping of wild-type (WT) and ZmELS5 near-isogenic lines (NILs) at V13 stage: (A) Whole plant of WT and ZmELS5 NILs at V13 stage; (B) the 11th leaf phenotype of the WT and ZmELS5 NILs at V13 stage.

Figure 2

Chlorophyll contents in the leaves of WT and ZmELS5 NILs.

Figure 3

Functional classification of differentially expressed genes. Red dots indicate up-regulated genes and green dots indicate down-regulated genes under significant levels of Padj <0.05 and Log₂ fold change >2.

Figure 4

(A) Gene ontology (GO) and (B) Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differentially expressed genes.

Figure 5

Gene and biological process connect network.

Figure 6

Different cellular components connect network.

Figure 7

Gene set enrichment analysis of cell component distribution.

Figure 8

Network of roles of cellular components enriched in gene sets.

Figure 9

Comparison of expression of WT and ZmELS5 NILs.

Figure 10

The string network of proteins (encoded by the differentially expressed genes (DEGs)) involved in senescence signaling pathways.

Figure 11

Predicting the regulatory process of premature senescence of mutant leaves.