Search

Nonstructural carbon (NSC), which represents the relationship between the carbon source and carbon sink, is an important factor that reflects the functions and performance of a tree. However, little is known regarding the time-series responses of NSC storage in evergreen species to different nitrogen (N) fertilization regimes. This study, which was based on a pot experiment, examined the response of the NSC (soluble sugars and starch) storage to different N addition intensities [light N addition (LN): 6.5 g N m−2 a−1; moderate N addition (MN): 13.0 g N m−2 a−1; and heavy N addition (HN): 26.0 g N m−2 a−1)] in saplings of the evergreen species Podocarpus macrophyllus. Our results showed that the net photosynthetic rate (Pn) under MN was significantly higher than that under LN, but was comparable to that under HN. Moreover, saplings subject to MN had a significant higher leaf biomass than that to LN and HN. These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN. The NSCs reserve under MN was considerable with that under LN, which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group. However, saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments. The leaf N concentrations were found in the increasing sequence of LN

Background The tree peony (Paeonia suffruticosa Andr.) cultivar ‘Er Qiao’ is appreciated for its unstable variegated flower coloration, with cyanic and acyanic flowers appearing on different branches of the same plant and occasionally in a single flower or petal. However, the variegation mechanism is still unclear. Results In this study, we found significantly higher contents and more diverse sets of anthocyanins in the cyanic petals than in the acyanic petals. Comparative transcriptome analysis between the two flower types revealed 477 differentially expressed genes (DEGs). Quantitative real-time PCR results verified that the transcript levels of the flavonol synthase (FLS) gene were significantly increased in the acyanic petals. Furthermore, we found that a GCGGCG insertion at 246 bp in the flavonoid 3′-hydroxylase (F3’H) gene-coding region constitutes a duplication of the 241–245 bp section and was consistently found only in acyanic flowers. Sequence alignment of the F3’H gene from different plant species indicated that only the acyanic petals of ‘Er Qiao’ contained the GCGGCG insertion. The transformation of Arabidopsis tt7–1 lines demonstrated that the ectopic expression of F3’H-cyanic, but not F3’H-acyanic, could complement the colors in the hypocotyl and seed coat. Conclusion In summary, we found that an indel in F3’H and the upregulation of FLS drastically reduced the anthocyanin content in acyanic petals. Our results provide molecular candidates for a better understanding of the variegation mechanisms in tree peony.

Background R2R3 myeloblastosis (MYB) genes are widely distributed in plants and comprise one of the largest transcription factor gene families. They play important roles in the regulatory networks controlling development, metabolism, and stress responses. Researches on functional genes in tree peony are still in its infancy. To date, few MYB genes have thus far been reported. Results In this study, we constructed a comprehensive reference gene set by transcriptome sequencing to obtain R2R3 MYB genes. The transcriptomes of eight different tissues were sequenced, and 92,837 unigenes were obtained with an N50 of 1662 nt. A total of 48,435 unigenes (77.98%) were functionally annotated in public databases. Based on the assembly, we identified 57 R2R3 MYB genes containing full-length open reading frames, which clustered into 35 clades by phylogenetic analysis. PsMYB57 clustered with anthocyanin regulation genes in Arabidopsis and was mainly transcribed in the buds and young leaves. The overexpression of PsMYB57 induced anthocyanin accumulation in tobacco, and four detected anthocyanin structural genes, including NtCHS, NtF3’H, NtDFR, and NtANS, were upregulated. The two endogenous bHLH genes NtAn1a and NtAn1b were also upregulated and may work in combination with PsMYB57 in regulating anthocyanin structural genes. Conclusions Our study offers a useful reference to the selection of candidate MYB genes for further functional studies in tree peony. Function analysis of PsMYB57 is helpful to understand the color accumulation in vegetative organs of tree peony. PsMYB57 is also a promising resource to improve plant color in molecular breeding.

Freshly consumed peaches ( Prunus persica L. Batsch) can cause allergic reactions in the worldwide population because of the presence of four classes of allergens (Pru p 1, Pru p 2, Pru p 3, and Pru p 4). Fruit bagging has been widely practiced in peach cultivation to improve fruit quality; however, its effect on the expression of peach allergen-encoding genes remains unknown. In this study, the influence of fruit bagging with opaque paper bags on the major peach allergen-encoding genes, including Pru p 1.01, Pru p 1.06B, Pru p 2.01B, Pru p 2.02, Pru p 3.01, Pru p 4.01, and Pru p 4.02, were measured by means of real-time PCR. A significant reduction in transcript accumulation was observed for all of the selected genes in the epicarps of the bagged peach fruits, whereas slight increases were observed in the mesocarps for these genes, with the two exceptions of Pru p 2.02 and Pru p 3.01. For most of these genes, much higher transcripts were determined in the epicarps than in the mesocarps. Taken together, a significant reduction in the transcription rate of the allergen-encoding genes in the whole peach fruit was achieved by shading with opaque paper bags. According to these data, modifications in growing practices of peach may help to obtain fruits with lower levels of allergens and thus contribute to reducing potential allergenic risks in consumers.

Thinning and understory removal, which are commonly used in forest management, are expected to affect litter decomposition. However, little is known about how litter decomposition rates change in stands subject to both thinning and understory removal. This knowledge gap is urgent to be filled because the two practices are often applied simultaneously. In the present study, an experiment containing a complete factorial combination of thinning and understory removal was arranged in a Chinese fir (Cunninghamia lanceolata) plantation. Litter decomposition rate was determined by using litter bags, and litter bags with different mesh sizes (0.1 mm and 2 mm) were used to identify the effect of soil mesofauna on decomposition. The temperature, moisture, and microbial abundance of surface soil were also measured. Results showed that thinning did not change litter decomposition rate, partly because of the unresponsive soil temperature, moisture, and abundance of microbial groups following thinning. Understory removal markedly restricted litter mass loss by more than 20%. Despite an obvious decrease in soil microbial abundance following understory removal, this should not account for why understory removal lowered litter decomposition rate, because this negative effect on litter mass loss disappeared when soil mesofauna was excluded. In addition, no interaction between thinning and understory removal was detected on litter decomposition. We emphasized that (1) Understory removal retard litter decomposition by suppressing the activity of soil mesofauna rather than by reducing microbial abundance; (2) Understory removal caused an equal reduction in litter mass loss regardless of thinning treatment. We believe that these results provide an important guidance for evaluating the effect of thinning and understory removal on some ecological processes associated with litter decomposition (i.e. soil formation and CO2 emission from the soil to the atmosphere) in a fir plantation.

How tree growth and the underlying photosynthesis of leaves, especially those multi-aged leaves, change after the application of both pruning and understory removal remains unclear. In this study, the tree growth and photosynthetic responses of various-aged needles to pruning, understory removal and their interactions were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. The biochemical and stomatal limitations to photosynthesis was separated by the combined measurements of stable carbon (δ 13C) and oxygen (δ 18O) isotopes in needles. Our results showed that the tree growth rates did not respond to pruning, understory removal, and their interactions. Pruning significantly stimulated the net photosynthetic rates (PA) and stomatal conductance (gs) of remaining foliage (especially the current- and one-year-needles). Although pruning had no effect on needle total nitrogen (N) concentration, the concentrations of water-soluble N (NS), the ratio of water-soluble N to sodium dodecyl sulfate (SDS)-insoluble N (NS/ND), and the photosynthetic N use efficiency (PNUE) were higher in needles of pruned trees compared with the unpruned trees. A significant and positive correlation between PNUE and NS/ND was also detected. The constant δ 13C and declined δ 18O in the current-year-needles from pruned trees suggested that both the photosynthetic capacity and the gs were responsible for the enhancement in PA of the youngest needles. Conversely, in the previous year needles, δ 13C and δ 18O were not significantly different between the control and pruned trees. Consistent with the response of tree growth rate, the foliar photosynthesis also did not exhibit changes following understory removal in both pruned and unpruned stands. We highlighted that pruning caused an up-regulation in PA of remaining foliage, thereby mitigating the negative effects of canopy loss on carbon assimilation.

Red leaf lettuce (Lactuca sativaL.) is popular due to its high anthocyanin content, but poor leaf coloring often occurs under low light intensity. In order to reveal the mechanisms of anthocyanins affected by light intensity, we compared the transcriptome ofL. sativaL. var.capitataunder light intensities of 40 and 100 μmol m−2s−1. A total of 62,111 unigenes were de novo assembled with an N50 of 1,681 bp, and 48,435 unigenes were functionally annotated in public databases. A total of 3,899 differentially expressed genes (DEGs) were detected, of which 1,377 unigenes were up-regulated and 2,552 unigenes were down-regulated in the high light samples. By Kyoto Encyclopedia of Genes and Genomes enrichment analysis, the DEGs were significantly enriched in 14 pathways. Using gene annotation and phylogenetic analysis, we identified seven anthocyanin structural genes, includingCHS,CHI,F3H,F3′H,DFR,ANS, and3GT, and two anthocyanin transport genes,GSTandMATE. In terms of anthocyanin regulatory genes, five MYBs and one bHLH gene were identified. AnHY5gene was discovered, which may respond to light-signaling and regulate anthocyanin structural genes. These genes showed a log2FC of 2.7–9.0 under high irradiance, and were validated using quantitative real-time-PCR. In conclusion, our results indicated transcriptome variance in red leaf lettuce under low and high light intensity, and observed a anthocyanin biosynthesis and regulation pattern. The data should further help to unravel the molecular mechanisms of anthocyanins influenced by light intensity.

Hydroxycinnamic acid amides (HCAAs) are a class of antimicrobial metabolites involved in plant defense against necrotrophic pathogens, including Alternaria brassicicola and Botrytis cinerea. The agmatine coumaryl transferase (AtACT) is the key enzyme that catalyzes the last reaction in the biosynthesis of HCAAs, including p-coumaroylagmatine (CouAgm) and feruloylagmatine in Arabidopsis thaliana. However, the regulatory mechanism of AtACT gene expression is currently unknown. Yeast one-hybrid screening using the AtACT promoter as bait isolated the key positive regulator ORA59 that is involved in jasmonic acid/ethylene (JA/ET)-mediated plant defense responses. AtACT gene expression and HCAAs biosynthesis were synergistically induced by a combination of JA and ET. In the AtACT promoter, two GCC-boxes function equivalently for trans-activation by ORA59 in Arabidopsis protoplasts, and mutation of either GCC-box abolished AtACT mRNA accumulation in transgenic plants. Site-directed mutation analysis demonstrated that the specific Leu residue at position 228 of the ORA59 EDLL motif mainly contributed to its transcriptional activity on AtACT gene expression. Importantly, MEDIATOR25 (MED25) and ORA59 homodimer are also required for ORA59-dependent activation of the AtACT gene. These results suggest that ORA59 and two functionally equivalent GCC-boxes form the regulatory module together with MED25 that enables AtACT gene expression and HCAAs biosynthesis to respond to simultaneous activation of the JA/ET signaling pathways.