Early Stages Of Seed Germination Research Articles

Genome-Wide Dissection of the MicroRNA Expression Profile in Rice Embryo during Early Stages of Seed Germination.

The first 24 hours after imbibition (HAI) is pivotal for rice seed germination, during which embryo cells switch from a quiescent state to a metabolically active state rapidly. MicroRNAs (miRNAs) have increasingly been shown to play important roles in rice development. Nevertheless, limited knowledge about miRNA regulation has been obtained in the early stages of rice seed germination. In this study, the small RNAs (sRNAs) from embryos of 0, 12, and 24 HAI rice seeds were sequenced to investigate the composition and expression patterns of miRNAs. The bioinformatics analysis identified 289 miRNA loci, including 59 known and 230 novel miRNAs, and 35 selected miRNAs were confirmed by stem-loop real-time RT-PCR. Expression analysis revealed that the dry and imbibed seeds have unique miRNA expression patterns compared with other tissues, particularly for the dry seeds. Using three methods, Mireap, psRNATarget and degradome analyses, 1197 potential target genes of identified miRNAs involved in various molecular functions were predicted. Among these target genes, 39 had significantly negative correlations with their corresponding miRNAs as inferred from published transcriptome data, and 6 inversely expressed miRNA-target pairs were confirmed by 5ʹ-RACE assay. Our work provides an inventory of miRNA expression profiles and miRNA-target interactions in rice embryos, and lays a foundation for further studies of miRNA-mediated regulation in initial seed germination.

Proteomic Analysis of Phosphoproteins in the Rice Nucleus During the Early Stage of Seed Germination.

The early stage of seed germination is the first step in the plant life cycle without visible morphological change. To investigate the mechanism controlling the early stage of rice seed germination, we performed gel-and label-free nuclear phosphoproteomics. A total of 3467 phosphopeptides belonging to 102 nuclear phosphoproteins from rice embryos were identified. Protein-synthesis-related proteins were mainly phosphorylated. During the first 24 h following imbibition, 115 nuclear phosphoproteins were identified, and significant changes in the phosphorylation level over time were observed in 29 phosphoproteins. Cluster analysis indicated that nucleotide-binding proteins and zinc finger CCCH- and BED-type proteins increased in abundance during the first 12 h of imbibition and then decreased. The in silico protein-protein interactions for 29 nuclear phosphoproteins indicated that the Sas10/Utp3 protein, which functions in snoRNA binding and gene silencing, was the center of the phosphoprotein network in nuclei. The germination rate of seeds was significantly slowed with phosphatase inhibitor treatment. The mRNA expression of the zinc finger CCCH-type protein did not change, and the zinc finger BED-type protein was upregulated in rice embryos during the early stage of germination with phosphatase inhibitor treatment. These results suggest that the phosphorylation and dephosphorylation of nuclear proteins are involved in rice seed germination. Furthermore, transcription factors such as zinc finger CCCH- and BED-type proteins might play a key role through nuclear phosphoproteins, and Sas10/Utp3 protein might interact with nuclear phosphoproteins in rice embryos to mediate the early stage of seed germination.

Comparative Proteomic Analysis of Embryos between a Maize Hybrid and Its Parental Lines during Early Stages of Seed Germination

In spite of commercial use of heterosis in agriculture, the molecular basis of heterosis is poorly understood. It was observed that maize hybrid Zong3/87-1 exhibited an earlier onset or heterosis in radicle emergence. To get insights into the underlying mechanism of heterosis in radicle emergence, differential proteomic analysis between hybrid and its parental lines was performed. In total, the number of differentially expressed protein spots between hybrid and its parental lines in dry and 24 h imbibed seed embryos were 134 and 191, respectively, among which 47.01% (63/134) and 34.55% (66/191) protein spots displayed nonadditively expressed pattern. Remarkably, 54.55% of nonadditively accumulated proteins in 24 h imbibed seed embryos displayed above or equal to the level of the higher parent patterns. Moreover, 155 differentially expressed protein spots were identified, which were grouped into eight functional classes, including transcription & translation, energy & metabolism, signal transduction, disease & defense, storage protein, transposable element, cell growth & division and unclassified proteins. In addition, one of the upregulated proteins in F1 hybrids was ZmACT2, a homolog of Arabidopsis thaliana ACT7 (AtACT7). Expressing ZmACT2 driven by the AtACT7 promoter partially complemented the low germination phenotype in the Atact7 mutant. These results indicated that hybridization between two parental lines can cause changes in the expression of a variety of proteins, and it is concluded that the altered pattern of gene expression at translational level in the hybrid may be responsible for the observed heterosis.

Effects of Exogenous Nitric Oxide Donor Sodium Nitroprusside on β-Amylase and Its Subcellular Localization during Early Stage of Seed Germination in Wheat

Nitric oxide(NO) is an important signaling molecule with diverse physiological functions in plants. NO can break dormancy of seeds,and promote seeds germination under various stresses and normal growth conditions. In this report,treatment with 0.5 mmol L-1 sodium nitroprusside(SNP) promoted seeds germination by increasing β-amylase activity,while the application of α-cyclodextrin,a specific inhibitor of β-amylase,could apparently inhibit the process induced by SNP. Semi-quantitative RT-PCR analysis indicated that the application of SNP induced the free β-amylase activity,and up-regulated β-amylase transcript. Western-blotting result showed that SNP increased the protein level of β-amylase,whereas the cPTIO(a specific scavenger of NO) and actinomycin-D(a transcriptional inhibitor) reversed changes in transcriptional and the protein levels mentioned above. Subcellular localization studies of proteins via immunoelectron microscopy technique illustrated that SNP could increase the quantity of β-amylase which was predominantly located in protein storage vacuole,and adhered to starch granules. The above results suggest that SNP might not only enhance the activity of free β-amylase,but also induce the β-amylase synthesis de novo at the early stage of wheat seed germination.

Polymorphism in rice amylases at an early stage of seed germination.

A polymorphism in rice amylases at an early stage of seed germination is analyzed by zymogram. In non-glutinous cultivars of rice, alpha-amylase isozymes are mainly confirmed in germinating seeds. However, in glutinous cultivars, beta-amylase isozymes, which are not confirmed in nonglutinous cultivars, make up the major part of the total amylase activity and the expression of alpha-amylases are repressed.

Mobilization of Reserve Proteins During Early Stages of Seed Germination in Fagopyrum Esculentum

Hydrolysis of 13S globulin, the main storage protein in grains of common buckwheat (Fagopyrum esculentum Moench), proceeds in at least two phases during germination. The first stage, involving a limited proteolytic cleavage of the protein, is associated with increased activity of proteases having maximum activity at pH 7.6. The second stage, involving further hydrolysis of the partially cleaved protein, starts after 12 h of imbibition. During this phase, activity of proteases increased and activity maximum shifted to pH 5.6. Nevertheless, 13S globulin retains its antigenic identity till the emergence of radicle and plumule. Thus, it may not be the major source of amino acids utilized by the germinating seed during the initial stages of imbibition.