Recent Advances in the Analysis of Cold Tolerance in Maize

Abstract

Maize (Zea mays L.) is an annual grass that originated in tropical and subtropical regions of the New World. Maize is highly sensitive to cold stress during seed gemination and the seedling phase, which can lead to reductions in plant vigor and grain production. There are large differences in the morphological and physiological changes caused by cold stress among maize varieties. In general, cold tolerant varieties have a stronger ability to maintain such changes in traits related to seed germination, root phenotypes, and shoot photosynthesis. These morphological and physiological characteristics have been widely used to evaluate the cold tolerance of maize varieties in genetic analyses. In recent years, considerable progress has been made in elucidating the mechanisms of maize in response to cold tolerance. Several QTL, GWAS, and transcriptomic analyses have been conducted on various maize genotypes and populations that show large variations in cold tolerance, resulting in the discovery of hundreds of candidate cold regulation genes. Nevertheless, only a few candidate genes have been functionally characterized. In the present review, we summarize recent progress in molecular, physiological, genetic, and genomic analyses of cold tolerance in maize. We address the advantages of joint analyses that combine multiple genetic and genomic approaches to improve the accuracy of identifying cold regulated genes that can be further used in molecular breeding. We also discuss the involvement of long-distance signaling in plant cold tolerance. These novel insights will provide a better mechanistic understanding of cold tolerance in maize.

Integrative Proteome and Phosphoproteome Profiling of Early Cold Response in Maize Seedlings

“…Cold temperature is a major environmental factor that limits the adaptation and growth of maize in temperate regions [ 1 ]. As a typical C 4 plant originated in tropical regions, maize ( Zea mays L.) has higher optimal growth temperature than C 3 plants, and is more sensitive to cold stress especially during seed germination and early seedling growth stages [ 1 , 2 , 3 , 4 ]. Increasing the cold tolerance is a major breeding goal for maize breeders, as it is a bottleneck to reach the high potential of maize production in temperate areas [ 5 ].…”

“…Much progress has been made in understanding the physiological response of cold stress in maize [ 1 , 3 , 17 ], but the genetic basis of the cold adaptation in maize remains poorly characterized [ 1 , 3 , 17 , 18 ]. Physiological and genetic studies suggest that chilling temperatures affect distinct metabolic functions at different maize growth stages, each under the control of independent gene sets [ 1 , 17 ].…”

“…Temperatures below 10 °C negatively affect gemination rate and slow seedling establishment [ 1 , 19 ]. During the seedling growth stage, chilling temperatures reduce chlorophyll content, decrease photosynthesis rate including photosystem II efficiency, retard growth, and induce oxygen species that would cause cellular and tissue damages [ 1 , 3 , 17 ]. Genetic mapping and GWAS analyses have identified a large number of quantitative trait loci (QTL) and single nucleotide polymorphisms (SNPs) associated with distinct traits of cold tolerance [ 3 , 17 ], and have uncovered a few underlying candidate genes with mostly minor effects on chilling tolerance [ 1 , 4 , 5 ].…”

“…During the seedling growth stage, chilling temperatures reduce chlorophyll content, decrease photosynthesis rate including photosystem II efficiency, retard growth, and induce oxygen species that would cause cellular and tissue damages [ 1 , 3 , 17 ]. Genetic mapping and GWAS analyses have identified a large number of quantitative trait loci (QTL) and single nucleotide polymorphisms (SNPs) associated with distinct traits of cold tolerance [ 3 , 17 ], and have uncovered a few underlying candidate genes with mostly minor effects on chilling tolerance [ 1 , 4 , 5 ]. Large scale RNA-seq analyses have identified thousands of genes responsive to cold stress in maize [ 3 , 20 , 21 , 22 , 23 ], but functional characterization of cold-responsive genes was limited, and genetic verification of implication of candidate genes in cold tolerance was mostly performed in Arabidopsis and tobacco [ 3 ].…”

“…Genetic mapping and GWAS analyses have identified a large number of quantitative trait loci (QTL) and single nucleotide polymorphisms (SNPs) associated with distinct traits of cold tolerance [ 3 , 17 ], and have uncovered a few underlying candidate genes with mostly minor effects on chilling tolerance [ 1 , 4 , 5 ]. Large scale RNA-seq analyses have identified thousands of genes responsive to cold stress in maize [ 3 , 20 , 21 , 22 , 23 ], but functional characterization of cold-responsive genes was limited, and genetic verification of implication of candidate genes in cold tolerance was mostly performed in Arabidopsis and tobacco [ 3 ]. However, recently, Zeng et al [ 18 ] reported that a mitogen-activated protein kinase ZmMPK8 phosphorylates a type-A Response Regulator 1 (ZmRR1) after cold stress, and showed that ZmMPK8 and ZmRR1 act as a negative and a positive regulator of cold tolerance in maize, respectively, using over-expression and CRISPR/Cas9-edited maize lines of each gene.…”