De novo characterization of Larix gmelinii (Rupr.) Rupr. transcriptome and analysis of its gene expression induced by jasmonates

Abstract

BackgroundLarix gmelinii is a dominant tree species in China’s boreal forests and plays an important role in the coniferous ecosystem. It is also one of the most economically important tree species in the Chinese timber industry due to excellent water resistance and anti-corrosion of its wood products. Unfortunately, in Northeast China, L. gmelinii often suffers from serious attacks by diseases and insects. The application of exogenous volatile semiochemicals may induce and enhance its resistance against insect or disease attacks; however, little is known regarding the genes and molecular mechanisms related to induced resistance.ResultsWe performed de novo sequencing and assembly of the L. gmelinii transcriptome using a short read sequencing technology (Illumina). Chemical defenses of L. gmelinii seedlings were induced with jasmonic acid (JA) or methyl jasmonate (MeJA) for 6 hours. Transcriptomes were compared between seedlings induced by JA, MeJA and untreated controls using a tag-based digital gene expression profiling system. In a single run, 25,977,782 short reads were produced and 51,157 unigenes were obtained with a mean length of 517 nt. We sequenced 3 digital gene expression libraries and generated between 3.5 and 5.9 million raw tags, and obtained 52,040 reliable reference genes after removing redundancy. The expression of disease/insect-resistance genes (e.g., phenylalanine ammonialyase, coumarate 3-hydroxylase, lipoxygenase, allene oxide synthase and allene oxide cyclase) was up-regulated. The expression profiles of some abundant genes under different elicitor treatment were studied by using real-time qRT-PCR.The results showed that the expression levels of disease/insect-resistance genes in the seedling samples induced by JA and MeJA were higher than those in the control group. The seedlings induced with MeJA elicited the strongest increases in disease/insect-resistance genes.ConclusionsBoth JA and MeJA induced seedlings of L. gmelinii showed significantly increased expression of disease/insect-resistance genes. MeJA seemed to have a stronger induction effect than JA on expression of disease/insect-resistance related genes. This study provides sequence resources for L. gmelinii research and will help us to better understand the functions of disease/insect-resistance genes and the molecular mechanisms of secondary metabolisms in L. gmelinii.

Studying Secondary Growth and Bast Fiber Development: The Hemp Hypocotyl Peeks behind the Wall

“…Methyl jasmonate and other JAs are also factors regulating the biosynthesis of cell wall building components (Pauwels et al, 2008; Men et al, 2013). This is notably the case for lignin: we have found that the expression of several methyl jasmonate-up-regulated genes peaks simultaneously with the active jasmonates content, namely orthologs of Arabidopsis MetS1, PAL2, C3H, CCoAOMT, HCT, CAD4 , and 4CL2 (Supplementary Table S6).…”

Exogenous phytohormones increase the accumulation of health-promoting metabolites, and influence the expression patterns of biosynthesis related genes and biological activity in Chinese cabbage (Brassica rapa spp. pekinensis)

“…3a). Similarly, PAL gene expression was significantly higher in JA or MeJA treated Larix gmelinii plants than in the control plants (Men et al, 2013), and PAL enzyme activity increased in exogenously ABA-treated tomato leaves (Song et al, 2011). Chalcone-flavanone isomerase (CHI) is involved in the primary stage of flavonoid biosynthesis, and contributes to plant adaptive and protective responses to environmental stress.…”

Forest Tree Genomics: Review of Progress

“…The dynamic transcriptome response to different exposure durations may vary depending on the nature of the stress. Genes implicated in stress response include enzymes of primary and secondary metabolisms such as • Genes encoding for lipoxygenase (LOX), allene oxide cyclase (AOS) and allene oxide synthase (AOC) were upregulated in insect-attacked, in mechanically wounded and in jasmonate-treated trees (Men, Yan, & Liu, 2013;Ralph et al, 2006). • Resistant trees may exhibit a greater transcriptomic response (more responsive genes) to biotic stress than susceptible trees.…”

“…For example, Adomas et al (2008) found the number of differentially expressed genes after inoculation with a nonpathogen decreased with the exposure times. • Genes involved in stress response and in secondary metabolism are strongly preferentially expressed in trees under biotic stresses (Adomas et al, 2008;Liu et al, 2013;Men et al, 2013;Ralph et al, 2006). For example , the proportion of differentially expressed genes between uninfected and infected trees with white pine blister rust was higher in resistant (3.4%) than in susceptible trees (2.4%).…”