Delineating the structural, functional and evolutionary relationships of sucrose phosphate synthase gene family II in wheat and related grasses

<p>Abstract</p> <p>Background</p> <p>Sucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway. In the monocotyledonous Poaceae, five <it>SPS </it>genes have been identified. Here we present a detailed analysis of the wheat <it>SPSII </it>family in wheat. A set of homoeologue-specific primers was developed in order to permit both the detection of sequence variation, and the dissection of the individual contribution of each homoeologue to the global expression of <it>SPSII</it>.</p> <p>Results</p> <p>The expression in bread wheat over the course of development of various sucrose biosynthesis genes monitored on an Affymetrix array showed that the <it>SPS </it>genes were regulated over time and space. <it>SPSII </it>homoeologue-specific assays were used to show that the three homoeologues contributed differentially to the global expression of <it>SPSII</it>. Genetic mapping placed the set of homoeoloci on the short arms of the homoeologous group 3 chromosomes. A resequencing of the A and B genome copies allowed the detection of four haplotypes at each locus. The 3B copy includes an unspliced intron. A comparison of the sequences of the wheat <it>SPSII </it>orthologues present in the diploid progenitors einkorn, goatgrass and <it>Triticum speltoides</it>, as well as in the more distantly related species barley, rice, sorghum and purple false brome demonstrated that intronic sequence was less well conserved than exonic. Comparative sequence and phylogenetic analysis of <it>SPSII </it>gene showed that false purple brome was more similar to <it>Triticeae </it>than to rice. Wheat - rice synteny was found to be perturbed at the SPS region.</p> <p>Conclusion</p> <p>The homoeologue-specific assays will be suitable to derive associations between SPS functionality and key phenotypic traits. The amplicon sequences derived from the homoeologue-specific primers are informative regarding the evolution of <it>SPSII </it>in a polyploid context.</p

The RNA-seq transcriptomic analysis reveals genes mediating salt tolerance through rapid triggering of ion transporters in a mutant barley.

Considering the complex nature of salinity tolerance mechanisms, the use of isogenic lines or mutants possessing the same genetic background albeit different tolerance to salinity is a suitable method for reduction of analytical complexity to study these mechanisms. In the present study, whole transcriptome analysis was evaluated using RNA-seq method between a salt-tolerant mutant line "M4-73-30" and its wild-type "Zarjou" cultivar at seedling stage after six hours of exposure to salt stress (300 mM NaCl). Transcriptome sequencing yielded 20 million reads for each genotype. A total number of 7116 transcripts with differential expression were identified, 1586 and 1479 of which were obtained with significantly increased expression in the mutant and the wild-type, respectively. In addition, the families of WRKY, ERF, AP2/EREBP, NAC, CTR/DRE, AP2/ERF, MAD, MIKC, HSF, and bZIP were identified as the important transcription factors with specific expression in the mutant genotype. The RNA-seq results were confirmed at several time points using qRT-PCR for some important salt-responsive genes. In general, the results revealed that the mutant accumulated higher levels of sodium ion in the root and decreased its transfer to the shoot. Also, the mutant increased the amount of potassium ion leading to the maintenance a high ratio [K+]/[Na+] in the shoot compared to its wild-type via fast stomata closure and consequently transpiration reduction under the salt stress. Moreover, a reduction in photosynthesis and respiration was observed in the mutant, resulting in utilization of the stored energy and the carbon for maintaining the plant tissues, which is considered as a mechanism of salt tolerance in plants. Up-regulation of catalase, peroxidase, and ascorbate peroxidase genes has resulted in higher accumulation of H2O2 in the wild-type compared to the mutant. Therefore, the wild-type initiated rapid ROS signals which led to less oxidative scavenging in comparison with the mutant. The mutant increased expression in the ion transporters and the channels related to the salinity to maintain the ion homeostasis. In overall, the results demonstrated that the mutant responded better to the salt stress under both osmotic and ionic stress phases and lower damage was observed in the mutant compared to its wild-type under the salt stress

Cold stress resilience of Iranian olive genetic resources: evidence from autochthonous genotypes diversity

Olive (Olea europaea L.) is one of the most cultivated tree species in Iran. This plant is characterized by its tolerance to drought, salt, and heat stresses while being vulnerable to frost. During the last decade, periods of frost have occurred several times in Golestan Province, in the northeast of Iran, which caused severe damage to olive groves. This study aimed to evaluate and individuate autochthonous Iranian olive varieties with regard to frost tolerance and good agronomic performance. For this purpose, 218 frost-tolerant olive trees were selected from 150,000 adult olive trees (15–25 years old), following the last harsh autumn of 2016. The selected trees were reassessed at different intervals, i.e., 1, 4, and 7 months after the cold stress in field conditions. Using 19 morpho-agronomic traits, 45 individual trees with relatively stable frost-tolerance were reevaluated and selected for this research. Ten highly discriminating microsatellite markers were used for the genetic profiling of the 45 selected olive trees, and, ultimately, five genotypes with the highest tolerance among 45 selected ones were placed in a cold room at freezing temperatures for image analyses of cold damage. The results of morpho-agronomic analyses evidenced no bark splitting or symptoms of leaf drop in the 45 cold-tolerant olives (CTOs). The oil content of the cold-tolerant trees comprised almost 40% of the fruit dry weight, highlighting the potential of these varieties for oil production. Moreover, through molecular characterization, 36 unique molecular profiles were individuated among the 45 analyzed CTOs that were genetically more similar to the Mediterranean olive cultivars than the Iranian ones. The present study demonstrated the high potential of local olive varieties, which would be promising and more suitable than commercial olive varieties, with regard to the establishment of olive groves under cold climate conditions. This could be a valuable genetic resource for future breeding activities to face climate changes

Distribution of TF families in comparison between the genotypes under the drought stress.

<p>(A) Up-regulated in the roots of Hashem (B) Up-regulated in the shoots of Hashem (C) Up-regulated in the roots of Bivanij and (D) Up-regulated in the shoots of Bivanij. (E) Heatmap showing expression profile of NAC transcription factor family across different samples.</p

Summary of Illumina sequencing data and mapped reads for the samples.

<p>Summary of Illumina sequencing data and mapped reads for the samples.</p

GO enrichment analysis of DEGs identified between the tolerant and the sensitive genotypes under the drought stress in the roots and the shoots.

<p>GO enrichment analysis of DEGs identified between the tolerant and the sensitive genotypes under the drought stress in the roots and the shoots.</p

Number of differentially expressed genes.

<p>Comparison between: (A) The treatments (B) The genotypes and (C) The tissues. (D) Venn diagram shows the overlapped genes by comparing the genotypes under the control and the drought treatments in the roots and the shoots.</p

Correlation of the expression values of the samples.

<p>(A) Dendogram depicting correlation among different samples based on global expression profiles. (B) Heatmap grouped the eight samples based on log₁₀ transformed FPKM (>400) of the highly expressed genes. Color scale shows high and low expressions as red and green, respectively.</p

Validation of the RNA-Seq using the qRT-PCR.

<p>(A) Close correlation (r² = 0.80) of 12 selected genes between two approaches. (B) Comparison of the RNA-Seq and the qRT-PCR considering the expression of the 12 selected genes in some combinations for instance.</p