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Aldose reductases (ARs) have been considered to play important roles in sorbitol biosynthesis, cellular detoxification and stress response in some plants. ARs from maize are capable of catalyzing the oxidation of sorbitol to glucose. However, little is known how maize ARs response to abiotic stresses. In this work, we cloned one isoform of maize ARs (ZmAR1), and furthermore we analyzed the roles of ZmAR1 in response to salt and drought stresses at both prokaryotic and eukaryotic levels. ZmAR1 encodes a putative 35 kDa protein that contains 310 amino acids. Under normal growth conditions, ZmAR1 was expressed in maize seedlings, and the highest expression level was found in leaves. But when seedlings were subjected to drought or salt treatment, the expression levels of ZmAR1 were significantly reduced. The constitutive expression of ZmAR1 increased the sensitivity of recombinant E. coli cells to drought and salt stresses compared with the control. Under salt and drought stresses, transgenic Arabidopsis lines displayed lower seed germination rate, shorter seedling root length, lower chlorophyll content, lower survival rate and lower antioxidant enzyme activity than wild type (WT) plants, but transgenic Arabidopsis had higher relative conductivity, higher water loss rate, and more MDA content than WT. Meanwhile, the introduction of ZmAR1 into Arabidopsis changed the expression levels of some stress-related genes. Taken together, our results suggested that ZmAR1 might act as a negative regulator in response to salt and drought stresses in Arabidopsis by reducing the sorbitol content and modulating the expression levels of some stress-related genes.

Additional file 3: Table S1. Different hormones concentrations between Chang7-2 and tc19.

Drought is a major yield-limiting factor in maize production. Osmotic stress was applied to two maize inbred lines with polyethylene glycol 6000 treatments. Proteins from the leaves were analyzed by two-dimensional gel electrophoresis and peptide mass fingerprinting at two time points, 24 and 48 h after osmotic stress. Thirty-five proteins were differentially expressed between control and treatment groups in the two maize inbred lines. In ‘Qi319’, a drought-tolerant inbred line, there were five up-regulated proteins at 24 h and 13 up-regulated and one down-regulated protein at 48 h. In drought-sensitive line ‘Zheng58’, 10 proteins were up-regulated at 24 h, while six proteins were up-regulated at 48 h. The 35 proteins were subjected to mass spectrometry and 17 proteins were successfully identified. These proteins were classified into six categories: photosynthesis-related, energy and metabolism, signaling pathways, protein synthesis, defense-related, and unclassified.

Backgrounds: Grain size is a key factor in crop yield that gradually develops after pollination. However, few studies have reported gene expression patterns in maize grain development using mutants. To investigate the developmental mechanisms of grain size, we analyzed a large-grain mutant, named TC19, at the morphological and transcriptome level at five stages corresponding to days after pollination (DAP).Results: After maturation, the grain length, width, and thickness in TC19 were greater than that in Chang 7-2 (control) and increased by 3.57%, 8.80%, and 3.88%, respectively. Further analysis showed that grain width in TC19 was lower than in Chang 7-2 at 7, 14, and 21 DAP, but greater than that in Chang 7-2 at 28 and 35 DAP, indicating that 21 to 28 DAP was the critical stage for kernel width development. For all five stages, the concentrations of indole-3-acetic acid and brassinosteroids were significantly higher in TC19 than in Chang 7-2. Gibberellin was higher at 7, 14, and 21 DAP, and cytokinin was higher at 21 and 35 DAP, in TC19 than in Chang 7-2. Through transcriptome analysis at 14, 21, and 28 DAP, we identified 2987, 2647, and 3209 differentially expressed genes (DEGs) between TC19 and Chang 7-2. Gene Ontology analysis indicated that most of the grain size–related genes corresponded to three aspects, including cell components, molecular functions, and biological processes. The Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that 77 DEGs were enriched in the plant hormone signal transduction pathway. We further analyzed several highly expressed candidate genes, including AO2, ARF3, and IAA15, which are involved in the synthesis of IAA; and DWF4 and XTH, which are involved in the synthesis of BR.Conclusions: Our results elucidated the mechanisms of grain size development at the grain-filling stage and have potential application in maize breeding.

Maize rough dwarf disease (MRDD) is a viral disease that causes substantial yield loss, especially in China’s summer planted maize area. Discovery of resistance genes would help in developing high-yielding resistant maize hybrids. Genome-wide association studies (GWASs) have advanced quickly and are now a powerful tool for dissecting complex genetic architectures. In this study, the disease severity index (DSI) of 292 maize inbred lines and an F6 linkage population were investigated across multiple environments for two years. Using the genotypes obtained from the Maize SNP 50K chip, a GWAS was performed with four analytical models. The results showed that 22 SNPs distributed on chromosomes 1, 3, 4, 6, 7 and 8 were significantly associated with resistance to MRDD (P