Characterization and Alternative Splicing Profiles of the Lipoxygenase Gene Family in Tea Plant (Camellia sinensis)

Abstract

Oxylipins, including jasmonic acid (JA) and volatiles, are important for signaling in plants, and these are formed by the lipoxygenase (LOX) enzyme family. There is a large gap in understanding of the underlying molecular basis of their roles in tea plants. Here, we identified 11 CsLOX genes from the tea plant (Camellia sinensis), and characterized their phylogeny, gene structure and protein features into three subclasses. We then examined their enzymatic activities, LOX expression and alternative splicing of transcripts during development and in response to abiotic or biotic stresses in tea plants. In vitro expressed protein assays showed that the CsLOX2, 3 and 9 enzymatically function to produce 9/13-HPOT, 13-HPOT and 9-HPOT, respectively. CsLOX2 and CsLOX9 green fluorescent protein (GFP) fusion proteins localized to chloroplasts and the cytoplasm, respectively. RNA sequencing, quantitative reverse transcription–PCR and Northern blot analysis suggested that CsLOX5, 6 and 9 were predominantly expressed in seeds, flowers and roots, respectively. CsLOX2, 3, 4, 6 and 7 were up-regulated after attack by the insect Ectropis oblique, while CsLOX1 was induced after infection with the pathogen Glomerella cingulata. CsLOX3, 7 and 10 were up-regulated by JA but not ABA or salicylic acid. Long-term cold stress down-regulated CsLOX expression while a short duration of cold induced the expression of CsLOX1, 6 and 7. Alternatively spliced transcripts of six CsLOX genes were dynamically regulated through time and varied in relative abundances under the investigated stresses; we propose a mechanism of competing or compensating regulation between isoforms. This study improves our understanding of evolution of LOXs and regulation of their diverse functions in plants.

Transcriptome and Phytochemical Analyses Provide New Insights Into Long Non-Coding RNAs Modulating Characteristic Secondary Metabolites of Oolong Tea (Camellia sinensis) in Solar-Withering

“…Four of these regulatory relationships were positive, whereas the other three were negative. Recent studies confirmed that JA/MeJA biosynthesis involves a series of genes, including LOX, AOS, AOC, OPR, ACX, and MFP2 (Wasternack and Feussner, 2018;Zhu et al, 2018). Among these genes, LOX mediates the first step of JA/MeJA biosynthesis.…”

Comprehensive profiling of alternative splicing landscape during cold acclimation in tea plant

“…In our previous study, we found that some AS events were tissue specific in stem and root; we also found that some AS isoforms were the major transcripts involved in the flavonoid synthesis pathway, which suggested AS is positively correlated with the contents of catechins [29]. We also reported that six CsLOXs (lipoxygenase) varied significantly in relative abundances under the different stresses [30]. However, these studies on AS emphasize largely on secondary metabolism.…”

“…These results were consistent with those of previous reports in other plant species [31]. During the sharp cooling treatment of tea plants, the numbers of AS events under low-temperatures [cold acclimation of 6 h at 10°C, day/night temperature (CS), cold acclimation of 7 days at 10/4°C, day/night temperature (CA1) and cold acclimation of 7 days at 4/0°C, day/ night temperature (CA2)] were significantly increased relative to AS events in those growing under normal temperature (NA, 25/20°C, day/night temperature); thus, the amount of CS (30,212), CA1 (30,325) and CA2 (30,552) was about 3000 more than NA (27,234), respectively. It is noteworthy that the number of AS events (24,616) tremendously decreased under temperature recovery condition compared with both CA treatment and NA groups, implying that many AS genes had adapted to low-temperature environment and resulted in reduced occurrence of AS events during DA (de-acclimation) of tea plant.…”

Transcriptional variation in glucosinolate biosynthetic genes and inducible responses to aphid herbivory on field-grownArabidopsis thaliana

“…To deal with various threats, plants can activate defense mechanisms only when necessary. Such inducible defenses are triggered by wounding and insect attacks through jasmonate (JA) signaling (Mewis et al 2005; Escobar-Bravo et al 2017; Tsuda 2017; Zhu et al 2018; Zhou et al 2018; Nakano et al 2018), while constitutive defenses are continuously expressed.…”