BackgroundAs a response to caterpillar feeding, poplar releases a complex mixture of volatiles which comprises several classes of compounds. Poplar volatiles have been reported to function as signals in plant-insect interactions and intra- and inter-plant communication. Although the volatile blend is dominated by mono- and sesquiterpenes, there is much to be learned about their formation in poplar.ResultsHere we report the terpene synthase (TPS) gene family of western balsam poplar (Populus trichocarpa) consisting of 38 members. Eleven TPS genes (PtTPS5-15) could be isolated from gypsy moth (Lymantria dispar)-damaged P. trichocarpa leaves and heterologous expression in Escherichia coli revealed TPS activity for ten of the encoded enzymes. Analysis of TPS transcript abundance in herbivore-damaged leaves and undamaged control leaves showed that seven of the genes, PtTPS6, PtTPS7, PtTPS9, PtTPS10, PtTPS12, PtTPS13 and PtTPS15, were significantly upregulated after herbivory. Gypsy moth-feeding on individual leaves of P. trichocarpa trees resulted in induced volatile emission from damaged leaves, but not from undamaged adjacent leaves. Moreover, the concentration of jasmonic acid and its isoleucine conjugates as well as PtTPS6 gene expression were exclusively increased in the damaged leaves, suggesting that no systemic induction occurred within the tree.ConclusionsOur data indicate that the formation of herbivore-induced volatile terpenes in P. trichocarpa is mainly regulated by transcript accumulation of multiple TPS genes and is likely mediated by jasmonates. The specific local emission of volatiles from herbivore-damaged leaves might help herbivore enemies to find their hosts or prey in the tree canopy.

BackgroundThe whitebacked planthopper (WBPH), Sogatella furcifera Horváth, is a serious rice pest in Asia. Ovicidal resistance is a natural rice defense mechanism against WBPH and is characterized by the formation of watery lesions (WLs) and increased egg mortality (EM) at the WBPH oviposition sites.ResultsThis study aimed to understand the genetic and molecular basis of rice ovicidal resistance to WBPH by combining genetic and genomic analyses. First, the ovicidal trait in doubled haploid rice lines derived from a WBPH-resistant cultivar (CJ06) and a WBPH-susceptible cultivar (TN1) were phenotyped based on the necrotic symptoms of the leaf sheaths and EM. Using a constructed molecular linkage map, 19 quantitative trait loci (QTLs) associated with WLs and EM were identified on eight chromosomes. Of them, qWL6 was determined to be a major QTL for WL. Based on chromosome segment substitution lines and a residual heterozygous population, a high-resolution linkage analysis further defined the qWL6 locus to a 122-kb region on chromosome 6, which was annotated to encode 20 candidate genes. We then conducted an Affymetrix microarray analysis to determine the transcript abundance in the CJ06 and TN1 plants. Upon WBPH infestation, 432 genes in CJ06 and 257 genes in TN1 were significantly up-regulated, while 802 genes in CJ06 and 398 genes in TN1 were significantly down-regulated. This suggests that remarkable global changes in gene expression contribute to the ovicidal resistance of rice. Notably, four genes in the 122-kb region of the qWL6 locus were differentially regulated between CJ06 and TN1 in response to the WBPH infestation, suggesting they may be candidate resistance genes.ConclusionsThe information obtained from the fine mapping of qWL6 and the microarray analyses will facilitate the isolation of this important resistance gene and its use in breeding WBPH-resistant rice.

BackgroundFlowering time greatly influences the adaptation of wheat cultivars to diverse environmental conditions and is mainly controlled by vernalization and photoperiod genes. In wheat cultivars from the Yellow and Huai Valleys, which represent 60%-70% of the total wheat production in China, the large-scale genotyping of wheat germplasms has not yet been performed in terms of vernalization and photoperiod response alleles, limiting the use of Chinese wheat germplasms to a certain extent.ResultsIn this study, 173 winter wheat cultivars and 51 spring wheat cultivars from China were used to identify allelic variations of vernalization and photoperiod genes as well as copy number variations of Ppd-B1 and Vrn-A1. Two new co-dominant markers were developed in order to more precisely examine Vrn-A1b, Vrn-B1a, and Vrn-B1b. Two novel alleles at the Vrn-B3 locus were discovered and were designated Vrn-B3b and Vrn-B3c. Vrn-B3b had an 890-bp insertion in the promoter region of the recessive vrn-B3 allele, and Vrn-B3c allele had 2 deletions (a 20-bp deletion and a 4-bp deletion) in the promoter region of the dominant Vrn-B3a allele. Cultivar Hemai 26 lacked the Vrn-A1 gene. RT-PCR indicated that the 890-bp insertion in the Vrn-B3b allele significantly reduced the transcription of the Vrn-B3 gene. Cultivars Chadianhong with the Vrn-B3b allele and Hemai 26 with a Vrn-A1-null allele possessed relatively later heading and flowering times compared to those of Yanzhan 4110, which harbored recessive vrn-B3 and vrn-A1 alleles. Through identification of photoperiod genes, 2 new polymorphism combinations were found in 6 winter wheat cultivars and were designated Hapl-VII and Hapl-VIII, respectively. Distribution of the vernalization and photoperiod genes indicated that all recessive alleles at the 4 vernalization response loci, truncated “Chinese Spring” Ppd-B1 allele at Ppd-B1 locus and Hapl-I at the Ppd-D1 locus were predominant in Chinese winter wheat cultivars.ConclusionThis study illustrated the distribution of vernalization and photoperiod genes and identified 2 new Vrn-B3 alleles, 1 Vrn-A1-null allele, and two new Ppd-D1 polymorphism combinations, using developed functional markers. Results of this study have the potential to provide useful information for screening relatively superior wheat cultivars for better adaptability and maturity.