Gibberellin-signaling pathways in plants

Germinating seed can sense low temperature for the floral transition and vernalization of winter rapeseed (Brassica rapa)

The hybrid production of winter rapeseed is limited by the difficult vernalization processes. Thus, floral regulation of winter rapeseed parental lines cannot be executed through selection of sowing time during hybrid production. Therefore, in this study, strong winter rapeseed was used as the material to analyse the floral transition mechanism of germinating seed vernalization. Results demonstrated that germinating seeds could sense low temperatures and complete vernalization following a low temperature treatment for 56.5 d with a 100 % vernalization rate. The regression equation between vernalization rate (y) and vernalization treatment days (x) was determined as y = 0.019x - 0.0765 (R² = 0.8529). When the vernalization treatment time was prolonged, the vernalization rate and fruiting ability increased rapidly, and variations were observed in the membrane lipid oxidation and physiological characteristics. Furthermore, at the prolonged treatment time of 10-50 d, the salicylic acid (SA) content continued to decrease, with values significantly lower than those of the control. SA content is significantly positively correlated with the level of BrFLC transcription and a significantly negatively correlated with the vernalization rate of germinating seeds. Moreover, the expressions of genes associated with SA biosynthesis, SA signal transduction, the flowering key negative regulators were suppressed and that of positive regulators were promoted during vernalization. These results suggest that SA as a floral repressor is involved in the regulation of the vernalization process of winter rapeseed germination seeds. In addition, SA may be related to the counting dosage of vernalization.

Genome-Wide Association Study for Nine Plant Architecture Traits in Sorghum

Sorghum [ (L) Moench], an important grain and forage crop, is receiving significant attention as a lignocellulosic feedstock because of its water-use efficiency and high biomass yield potential. Because of the advancement of genotyping and sequencing technologies, genome-wide association study (GWAS) has become a routinely used method to investigate the genetic mechanisms underlying natural phenotypic variation. In this study, we performed a GWAS for nine grain and biomass-related plant architecture traits to determine their overall genetic architecture and the specific association of allelic variants in gibberellin (GA) biosynthesis and signaling genes with these phenotypes. A total of 101 single-nucleotide polymorphism (SNP) representative regions were associated with at least one of the nine traits, and two of the significant markers correspond to GA candidate genes, () and (), affecting plant height and seed number, respectively. The resolution of a previously reported quantitative trait loci (QTL) for leaf angle on chromosome 7 was increased to a 1.67 Mb region containing seven candidate genes with good prospects for further investigation. This study provides new knowledge of the association of GA genes with plant architecture traits and the genomic regions controlling variation in leaf angle, stem circumference, internode number, tiller number, seed number, panicle exsertion, and panicle length. The GA gene affecting seed number variation () and the genomic region on chromosome 7 associated with variation in leaf angle are also important outcomes of this study and represent the foundation of future validation studies needed to apply this knowledge in breeding programs.

Transcription profile of soybean-root-knot nematode interaction reveals a key role of phythormones in the resistance reaction

BACKGROUND

Root-knot nematodes (RKN- Meloidogyne genus) present extensive challenges to soybean crop. The soybean line (PI 595099) is known to be resistant against specific strains and races of nematode species, thus its differential gene expression analysis can lead to a comprehensive gene expression profiling in the incompatible soybean-RKN interaction. Even though many disease resistance genes have been studied, little has been reported about phytohormone crosstalk on modulation of ROS signaling during soybean-RKN interaction.

RESULTS

Using 454 technology to explore the common aspects of resistance reaction during both parasitism and resistance phases it was verified that hormone, carbohydrate metabolism and stress related genes were consistently expressed at high levels in infected roots as compared to mock control. Most noteworthy genes include those encoding glycosyltransferases, peroxidases, auxin-responsive proteins and gibberellin-regulated genes. Our data analysis suggests the key role of glycosyltransferases, auxins and components of gibberellin signal transduction, biosynthesis and deactivation pathways in the resistance reaction and their participation in jasmonate signaling and redox homeostasis in mediating aspects of plant growth and responses to biotic stress.

CONCLUSIONS

Based on this study we suggest a reasonable model regarding to the complex mechanisms of crosstalk between plant hormones, mainly gibberellins and auxins, which can be crucial to modulate the levels of ROS in the resistance reaction to nematode invasion. The model also includes recent findings concerning to the participation of DELLA-like proteins and ROS signaling controlling plant immune or stress responses. Furthermore, this study provides a dataset of potential candidate genes involved in both nematode parasitism and resistance, which can be tested further for their role in this biological process using functional genomics approaches.