Cloning and characterization of a novel barley gene,HvORG4,induced by Fusarium graminearum infection

Barley Fusarium head blight(FHB),caused by species of the Fusarium fungus,is a devastating disease that is reemerging worldwide in recent years.In this study,a novel gene,HvORG4,was cloned from barley by using cDNA library and suppression subtractive hybridization(SSH) library strategies.The SSH library and cDNA library were constructed from the Chinese barley cultivar Jing02-461(resistance to FHB) infected by Fusarium graminearum isolate Huanggang-1.For the SSH analysis,more than 120 differentially expressed cDNAs were identified and sequenced.One of them showed high homology to the AtORG4 gene and was used as a probe to screen the cDNA library of Jing02-461.Six positive clones were identified and one of them contained a full-length cDNA,which was named HvORG4.Sequence analysis showed that HvORG4 encoded a deduced basic protein of 197 amino acids.Northern blotting analysis showed that HvORG4 was constitutively expressed in root and stalk,not in leaf or spike,and strongly induced in barley spikelets in response to infection with F.graminearum isolate Huanggang-1.Its homology and expression profile suggest that the HvORG4 might function as a transcription factor,playing an important role in signal transduction pathway for defense against FHB in barley.

Transcriptional responses of Brassica nigra to feeding by specialist insects of different feeding guilds

Plants show phenotypic changes when challenged with herbivorous insects. The mechanisms underlying these changes include the activation of transcriptional responses, which are dependent on the attacking insect. Most transcriptomic studies on crucifer-insect interactions have focused on the model plant Arabidopsis thaliana, a species that faces low herbivore pressure in nature. Here, we study the transcriptional responses of plants from a wild black mustard （Brassica nigra） population to herbivores of different feeding guilds using an A. thaliana-based whole-genome microarray that has previously been shown to be suitable for transcriptomic analyses in Brassica. Transcriptional responses of B. nigra after infestation with either Pieris rapae caterpillars or Brevicoryne brassicae aphids are analyzed and compared. Additionally, the insect-induced expression changes of some individual genes are analyzed through quantitative real-time polymerase chain reaction. The results show that feeding by both insect species results in the accumulation of transcripts encoding proteins involved in the detoxification of reactive oxygen species, defensive proteins and glucosinolates and this is correlated with experimental evidence in the literature on such biochemical effects. Although genes encoding proteins involved in similar processes are regulated by both insects, there was little overlap in the induction or repression of individual genes. Furthermore, P. rapae and B. brassicae seem to affect different phytohormone signaling pathways. In conclusion, our results indicate that B. nigra activates several defense-related genes in response to P rapae or B. brassicae feeding, but that the response is dependent on the attacking insect species.