Biologia futura: the role of polyamine in plant science.

Polyamines (PAs) are positively charged amines such as putrescine, spermidine and spermine that ubiquitously exist in all organisms. They have been considered as a new type of plant biostimulants, with pivotal roles in many physiological processes. Polyamine levels are controlled by intricate regulatory feedback mechanisms. PAs are directly or indirectly regulated through interaction with signaling metabolites (H202, NO), aminobutyric acid (GABA), phytohormones (abscisic acid, gibberellins, ethylene, cytokinins, auxin, jasmonic acid and brassinosteroids) and nitrogen metabolism (maintaining the balance of C:N in plants). Exogenous applications of PAs enhance the stress resistance, flowering and fruit set, synthesis of bioactive compounds and extension of agricultural crops shelf life. Up-regulation of PAs biosynthesis by genetic manipulation can be a novel strategy to increase the productivity of agricultural crops. Recently, the role of PAs in symbiosis relationships between plants and beneficial microorganisms has been confirmed. PA metabolism has also been targeted to design new harmless fungicides.

Assessment of the vacuolar Na+/H+ antiporter (NHX1) transcriptional changes in Leptochloa fusca L. in response to salt and cadmium stresses.

Sodium/proton exchangers (NHX) are key players in plant responses to salinity and have a central role in establishing ion homeostasis. NHXs can be localized in tonoplast or plasma membranes, where they exchange sodium ions for protons, resulting in the removal of ions from the cytosol into vacuole or extracellular spaces. In the present study, the expression pattern of the gene encoding Na+/H+ antiporter in the vacuolarmembrane (NHX1 gene) in Leptochloa fusca (Kallar grass) was measured by a semi- quantitative RT-PCR method under different treatments of NaCl and CdCl2. Results indicated that NaCl positively affected expression levels of LfNHX1, and that the amount of LfNHX1 mRNA increased in conjunction with the rise of salinity pressure, This finding suggests that vacuolar Na+/H+ antiporter might play an important role in the salt tolerance ability of kallar grass. The results also showed that cadmium exposure significantly modulated the mRNA expression of the LfNHX1 gene, suggesting that cadmium exposure disturbed Na+ homeostasis across the tonoplast and decreased the salt tolerance ability of kallar grass.

Construction of an almond linkage map in an Australian population Nonpareil x Lauranne.

BACKGROUND: Despite a high genetic similarity to peach, almonds (Prunus dulcis) have a fleshless fruit and edible kernel, produced as a crop for human consumption. While the release of peach genome v1.0 provides an excellent opportunity for almond genetic and genomic studies, well-assessed segregating populations and the respective saturated genetic linkage maps lay the foundation for such studies to be completed in almond. RESULTS: Using an almond intraspecific cross between 'Nonpareil' and 'Lauranne' (N x L), we constructed a moderately saturated map with SSRs, SNPs, ISSRs and RAPDs. The N x L map covered 591.4 cM of the genome with 157 loci. The average marker distance of the map was 4.0 cM. The map displayed high synteny and colinearity with the Prunus T x E reference map in all eight linkage groups (G1-G8). The positions of 14 mapped gene-anchored SNPs corresponded approximately with the positions of homologous sequences in the peach genome v1.0. Analysis of Mendelian segregation ratios showed that 17.9% of markers had significantly skewed genotype ratios at the level of P < 0.05. Due to the large number of skewed markers in the linkage group 7, the potential existence of deleterious gene(s) was assessed in the group. Integrated maps produced by two different mapping methods using JoinMap® 3 were compared, and their high degree of similarity was evident despite the positional inconsistency of a few markers. CONCLUSIONS: We presented a moderately saturated Australian almond map, which is highly syntenic and collinear with the Prunus reference map and peach genome V1.0. Therefore, the well-assessed almond population reported here can be used to investigate the traits of interest under Australian growing conditions, and provides more information on the almond genome for the international community.

Mapping SNP-anchored genes using high-resolution melting analysis in almond.

Peach and almond have been considered as model species for the family Rosaceae and other woody plants. Consequently, mapping and characterisation of genes in these species has important implications. High-resolution melting (HRM) analysis is a recent development in the detection of SNPs and other markers, and proved to be an efficient and cost-effective approach. In this study, we aimed to map genes corresponding to known proteins in other species using the HRM approach. Prunus unigenes were searched and compared with known proteins in the public databases. We developed single-nucleotide polymorphism (SNP) markers, polymorphic in a mapping population produced from a cross between the cloned cultivars Nonpareil and Lauranne. A total of 12 SNP-anchored putative genes were genotyped in the population using HRM, and mapped to an existing linkage map. These genes were mapped on six linkage groups, and the predicted proteins were compared to putative orthologs in other species. Amongst those genes, four were abiotic stress-responsive genes, which can provide a starting point for construction of an abiotic resistance map. Two allergy and detoxification related genes, respectively, were also mapped and analysed. Most of the investigated genes had high similarities to sequences from closely related species such as apricot, apple and other eudicots, and these are putatively orthologous. In addition, it was shown that HRM can be an effective means of genotyping populations for the purpose of constructing a linkage map. Our work provides basic genomic information for the 12 genes, which can be used for further genetic and functional studies.