Kui Xiang

Cloning and characterization of miRNAs from maize seedling roots under low phosphorus stress

MicroRNAs (miRNAs) are a class of small, non-coding regulatory RNAs that regulate gene expression by guiding target mRNA cleavage or translational inhibition in plants and animals. In this study, a small RNA library was constructed to identify conserved miRNAs as well as novel miRNAs in maize seedling roots under low level phosphorus stress. Twelve miRNAs were identified by high throughput sequencing of the library and subsequent analysis, two belong to conserved miRNA families (miRNA399b and miRNA156), and the remaining ten are novel and one of latter is conserved in gramineous species. Based on sequence homology, we predicted 125 potential target genes of these miRNAs and then expression patterns of 7 miRNAs were validated by semi-RT-PCR analysis. MiRNA399b, Zma-miR3, and their target genes (Zmpt1 and Zmpt2) were analyzed by real-time PCR. It is shown that both miRNA399b and Zma-miR3 are induced by low phosphorus stress and regulated by their target genes (Zmpt1 and Zmpt2). Moreover, Zma-miR3, regulated by two maize inorganic phosphate transporters as a newly identified miRNAs, would likely be directly involved in phosphate homeostasis, so was miRNA399b in Arabidopsis and rice. These results indicate that both conserved and maize-specific miRNAs play important roles in stress responses and other physiological processes correlated with phosphate starvation, regulated by their target genes. Identification of these differentially expressed miRNAs will facilitate us to uncover the molecular mechanisms underlying the progression of maize seedling roots development under low level phosphorus stress.

Characterization of correlation between grain moisture and ear rot resistance in maize by QTL meta-analysis

Ear rot (ER) in maize is a prevalent disease worldwide which reduces yield and grain quality. Grain moisture content (GM) is an important factor which impacts the fungal development of ER species. Our purpose was to identify the genomic regions of maize in the control of GM and ER resistance, and the correlations between two traits. A meta-analysis was carried out using 241 quantitative trait loci (QTL) from 29 studies to propose meta-QTL (MQTL) on a high-density genetic linkage map (IBM 2 neighbors 2008). For GM content, 44 MQTL were identified on all chromosomes except for chromosome 9, while 29 MQTL were found for ER resistance, mainly located on chromosomes 3, 6 and 7. Moreover, 14 overlapping domains for GM MQTL and ER MQTL were observed on chromosomes 2, 3, 6 and 7, mainly focused on five active regions (bins 2.08–2.09, 3.04, 3.06, 6.04–6.06 and 7.03–7.03). There were 13 genes in the overlapping domain which could be divided into five classes: stress-related gene, photosystem-related gene, architecture-related gene, dynamic-related gene and seminal-related gene. It was possibly that the five-class genes were simultaneously related with GM and ER.

Difference between Pb and Cd accumulation in 19 elite maize inbred lines and application prospects

In the last two decades, the accumulation of heavy metal in crop grains has become the study hotspot. In this study, 19 representative elite maize inbred lines and 3 hybrid varieties were investigated at the seedling stage, which can accumulate Pb and Cd in the stems and leaves, respectively. The results demonstrated that significant differences are among inbred lines for accumulation of heavy metals, implying that the Cd accumulation is significant correlation between the male parents and their hybrids and some inbred lines have been selected for cross-breeding with low Pb or Cd accumulation, such as S37, 9782, and ES40; Moreover, some inbred lines could be suitable for phytoremediation species for soil bioremediation with high levels of Pb and Cd accumulation, including 178, R08, 48-2, and Mo17ht.

Different Gene Expressions of Resistant and Susceptible Maize Inbreds in Response to Fusarium verticillioides Infection

Ear rot, caused by Fusarium verticillioides (FV), is a destructive disease of maize as it reduces grain yield and increases risks of mycotoxin production, thus endangering livestock. To identify genes differentially expressed during FV infection, four cDNA libraries were constructed for suppression subtractive hybridization using RNA isolated from bracts of an FV-resistant inbred maize line, Bt-1, as well as an FV-susceptible maize inbred line, Ye478. A total of 145 clones were obtained following reverse dot-blot hybridization, and these were sequenced from these libraries. Similarity analysis revealed that of these genes, 93 were unique, including 68 of known function, 24 of unknown function, and a single novel gene. Most genes of known function were predominantly involved in plant defense such as cell defense, transcription regulation, signal transduction, and metabolism. Expression profiles of eight representative genes, using semiquantitative reverse transcription-polymerase chain reaction, confirmed that differential gene regulation during FV infection was involved. These findings suggested that these differentially expressed genes might be involved in FV defense responses in maize.