Label-free quantitative proteomics of maize roots from different root zones provides insight into proteins associated with enhance water uptake.

BACKGROUND: Maize is one of the most important food crops worldwide. Roots play important role in maize productivity through water and nutrient uptake from the soil. Improving maize root traits for efficient water uptake will help to optimize irrigation and contribute to sustainable maize production. Therefore, we investigated the protein profiles of maize cv. Anyu308 root system divided into Upper root zone (UR), Middle root (MR), and Lower root (LR), by label free quantitative shotgun proteomic approach (LFQ). The aim of our study was to identify proteins and mechanisms associated with enhanced water uptake in different maize root zones under automatic irrigation system. RESULTS: At field capacity, MR had the highest water uptake than the UR and LR. We identified a total of 489 differentially abundant proteins (DAPs) by pairwise comparison of MR, LR, and UR. Cluster analysis of DAPs revealed MR and UR had similar protein abundance patterns different from LR. More proteins were differentially abundant in MR/UR compared to LR/MR and LR/UR. Comparisons of protein profiles indicate that the DAPs in MR increased in abundance, compared to UR and LR which had more downregulated DAPs. The abundance patterns, functional category, and pathway enrichment analyses highlight chromatin structure and dynamics, ribosomal structures, polysaccharide metabolism, energy metabolism and transport, induction of water channels, inorganic ion transport, intracellular trafficking, and vesicular transport, and posttranslational modification as primary biological processes related to enhanced root water uptake in maize. Specifically, the abundance of histones, ribosomal proteins, and aquaporins, including mitochondrion electron transport proteins and the TCA cycle, underpinned MR's enhanced water uptake. Furthermore, proteins involved in folding and vascular transport supported the radial transport of solute across cell membranes in UR and MR. Parallel reaction monitoring analysis was used to confirmed profile of the DAPs obtained by LFQ-based proteomics. CONCLUSION: The list of differentially abundant proteins identified in MR are interesting candidates for further elucidation of their role in enhanced water uptake in maize root. Overall, the current results provided an insight into the mechanisms of maize root water uptake.

Molecular mapping of quantitative trait loci for grain moisture at harvest and field grain drying rate in maize (Zea mays L.).

Maize (Zea mays L.) grain moisture (GM) at harvest is an important trait that affects seed preservation during storage, grain quality and artificial drying costs. To date, most of the work on understanding GM dynamics in maize has focused on the grain filling period, while the period of postmaturity grain drying remains unexplored. The field grain drying rate (FDR) is one of the most important factors in determining GM at harvest. Therefore, understanding the genetic basis of FDR will be useful for obtaining low-GM varieties. In this study, a single-cross population (330 F2:3 -generation plants) derived from a cross of two divergent inbred lines was evaluated in two planting environments with a measurement method - Area under the Dry Down Curve (AUDDC). A high-density genetic linkage map of 2491 single nucleotide polymorphism (SNP) loci covering 2415.56 cM was constructed. Using composite interval mapping, four quantitative trait loci (QTL), q45dGM1-1, qHTGM2-2, qAUDDC2-1 and qAUDDC10-1, which were detected on chromosomes 1, 2 and 10, were stable across environments and could explain more than 10% of phenotypic variance. These may be the major QTLs, with non-significant environmental interactions for GM at 45 days, GM at harvest and FDR, respectively. Additionally, several predicted candidate genes for FDR were identified, including several transcription factors, hormone responsive genes, energy-related and DNA replication-related genes. These results will provide useful information for our understanding of the genetic basis of FDR, as well as providing tools for marker-assisted selection in maize breeding.