Utilizing transcriptomics and metabolomics to unravel key genes and metabolites of maize seedlings in response to drought stress.

BACKGROUND: Drought stress can substantially restrict maize growth and productivity, and global warming and an increasing frequency of extreme weather events are likely to result in more yield losses in the future. Therefore, unraveling the molecular mechanism underlying the response to drought stress is essential for breeding drought-resilient crops. RESULTS: In this study, we subjected the 3-leaf-period plants of two maize inbred lines, a drought-tolerant line (si287) and a drought-sensitive line (X178), to drought stress for seven days while growing in a chamber. Subsequently, we measured physiological traits and analyzed transcriptomic and metabolic profiles of two inbred lines. Our KEGG analysis of genes and metabolites revealed significant differences in pathways related to glycolysis/gluconeogenesis, flavonoid biosynthesis, starch and sucrose metabolism, and biosynthesis of amino acids. Additionally, our joint analysis identified proline, tryptophan and phenylalanine are crucial amino acids for maize response to drought stress. Furthermore, we concentrated on tryptophan (Trp), which was found to enhance tolerance via IAA-ABA signaling, as well as SA and nicotinamide adenine dinucleotide (NAD) consequent reactive oxygen species (ROS) scavenging. We identified three hub genes in tryptophan biosynthesis, indole-3-acetaldehyde oxidase (ZmAO1, 542,228), catalase 1 (ZmCAT1, 542,369), and flavin-containing monooxygenase 6 (ZmYUC6, 103,629,142), High expression of these genes plays a significant role in regulating drought tolerance. Two metabolites related to tryptophan biosynthesis, quinolinic acid, and kynurenine improved maize tolerance to drought stress by scavenging reactive oxygen species. CONCLUSIONS: This study illuminates the mechanisms underlying the response of maize seedlings to drought stress. Especially, it identifies novel candidate genes and metabolites, enriching our understanding of the role of tryptophan in drought stress. The identification of distinct resistance mechanisms in maize inbred lines will facilitate the exploration of maize germplasm and the breeding of drought-resilient hybrids.

AMMI an GGE biplot analysis of grain yield for drought-tolerant maize hybrid selection in Inner Mongolia.

Due to the ongoing global warming, maize production worldwide is expected to be heavily inflicted by droughts. The grain yield of maize hybrids is an important factor in evaluating their suitability and stability. In this study, we utilized the AMMI model and GGE biplot to analyze grain yield of 20 hybrids from the three tested environments in Inner Mongolia in 2018 and 2019, aiming at selecting drought-tolerant maize hybrids. AMMI variance analysis revealed highly significant difference on main effects for genotype, environment, and their interaction. Furthermore, G11 (DK159) and G15 (JKY3308) exhibited favorable productivity and stability across all three test environments. Moreover, G10 (LH1) emerged as the most stable hybrid according to the AMMI analysis and the GGE biplot. Bayannur demonstrated the highest identification ability among the three tested sites. Our study provides accurate identification for drought-resilient maize hybrids in different rain-fed regions. These findings can contribute to the selection of appropriate hybrids that exhibit productivity, stability, and adaptability in drought-prone conditions.

Hymenobacter terrenus sp. nov., isolated from biological soil crusts.

A Gram-stain-negative, non-spore-forming, short rod-shaped, non-motile, light-pink bacterial strain, MIMtkLc17T, was isolated from biological soil crusts collected in Liangcheng, Inner Mongolia. Growth of strain MIMtkLc17T was observed at 2-35 °C and in the presence of 1% (w/v) NaCl. Phylogenetic analysis of 16S rRNA gene sequences showed that sequence similarities between strain MIMtkLc17T and the type strains of species of the genus Hymenobacter ranged from 89.93% to 96.49%. Strain MIMtkLc17T can secrete mass polysaccharide. The major fatty acids of strain MIMtkLc17T were iso-C15 : 0, summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), C16 : 1ω5c and summed feature 4 (iso-C17 : 1 I/anteiso-C17 : 1 B). The sole respiratory quinone was menaquinone MK-7. The G+C content of the chromosomal DNA was 57.8 mol%. The results of phylogenetic, chemotaxonomic and phenotypic characterization indicated that strain MIMtkLc17T can be distinguished from all known species of the genus Hymenobacter and represents a novel species of this genus, for which the name Hymenobacter terrenus sp. nov. is proposed. The type strain is MIMtkLc17T ( = MCCC 1K00507T = KCTC 42636T).