RNA-Seq Analysis Reveals MAPKKK Family Members Related to Drought Tolerance in Maize.

Ricardo Aroca,Ya Liu,Wen Ren,Fengling Yang,Hang He,Jiuran Zhao,Miaoyi Zhou,Zhaoxu Gao

doi:10.1371/journal.pone.0143128

Abstract

The mitogen-activated protein kinase (MAPK) cascade is an evolutionarily conserved signal transduction pathway that is involved in plant development and stress responses. As the first component of this phosphorelay cascade, mitogen-activated protein kinase kinase kinases (MAPKKKs) act as adaptors linking upstream signaling steps to the core MAPK cascade to promote the appropriate cellular responses; however, the functions of MAPKKKs in maize are unclear. Here, we identified 71 MAPKKK genes, of which 14 were novel, based on a computational analysis of the maize (Zea mays L.) genome. Using an RNA-seq analysis in the leaf, stem and root of maize under well-watered and drought-stress conditions, we identified 5,866 differentially expressed genes (DEGs), including 8 MAPKKK genes responsive to drought stress. Many of the DEGs were enriched in processes such as drought stress, abiotic stimulus, oxidation-reduction, and metabolic processes. The other way round, DEGs involved in processes such as oxidation, photosynthesis, and starch, proline, ethylene, and salicylic acid metabolism were clearly co-expressed with the MAPKKK genes. Furthermore, a quantitative real-time PCR (qRT-PCR) analysis was performed to assess the relative expression levels of MAPKKKs. Correlation analysis revealed that there was a significant correlation between expression levels of two MAPKKKs and relative biomass responsive to drought in 8 inbred lines. Our results indicate that MAPKKKs may have important regulatory functions in drought tolerance in maize.

Highlights

The world population is increasing at an alarming rate, while abiotic stresses play crucial roles in crop failures and reductions in field crop productivity
These reported mitogen-activated protein kinase kinase kinases (MAPKKKs) were named according to the foregoing study [57], while since there was no standard nomenclature followed for MAPKKKs neither in Arabidopsis nor in rice, the 14 putative MAPKKKs were designated according to their group (Table A in S1 File).We obtained the chromosomal locations of these 71 MAPKKKs, and the predicted subcellular localization was determined from the CELLO v2.5 server (Table A in S1 File)
The physical location data showed that 70 MAPKKKs were distributed on all 10 maize chromosomes (Fig 1D), except the GRMZM2G011070 (ZmMAPKKK29) gene, which was situated on an undetermined chromosome

Summary

Introduction

The world population is increasing at an alarming rate, while abiotic stresses play crucial roles in crop failures and reductions in field crop productivity. A total of 524 non-synonymous single nucleotide polymorphisms (nsSNPs) that were associated with 271 candidate genes for drought tolerance involved in plant hormone regulation, carbohydrate and sugar metabolism, signaling molecules regulation, redox reaction and acclimation of photosynthesis to environment were detected by common variants (CV) and cluster analyses with the availability of maize B73 reference genome and whole-genome resequencing of 15 maize inbred lines [4]. These selected genes will facilitate our understanding of the genetic basis of the drought stress response but will accelerate genetic improvement through marker-assisted selection in maize

Methods

Results

Conclusion