Molecular Horticulture最新文献

Medicinal plants represent a huge reservoir of secondary metabolites (SMs), substances with significant pharmaceutical and industrial potential. However, obtaining secondary metabolites remains a challenge due to their low-yield accumulation in medicinal plants; moreover, these secondary metabolites are produced through tightly coordinated pathways involving many spatiotemporally and environmentally regulated steps. The first regulatory layer involves a complex network of transcription factors; a second, more recently discovered layer of complexity in the regulation of SMs is epigenetic modification, such as DNA methylation, histone modification and small RNA-based mechanisms, which can jointly or separately influence secondary metabolites by regulating gene expression. Here, we summarize the findings in the fields of genetic and epigenetic regulation with a special emphasis on SMs in medicinal plants, providing a new perspective on the multiple layers of regulation of gene expression.

Volatile terpenes are important compounds that influence fruit flavour and aroma of kiwifruit. Terpenes in plants also impact on the floral bouquet and defence against pests and pathogens in leaves and fruit. To better understand the overlapping roles that terpenes may fulfil in plants, a systematic gene, chemical and biochemical analysis of terpenes and terpene synthases (TPS) was undertaken in Red5 kiwifruit (Actinidia spp.). Analysis of the Red5 genome shows it contains only 22 TPS gene models, of which fifteen encode full-length TPS. Thirteen TPS can account for the major terpene volatiles produced in different tissues of Red5 kiwifruit and in response to different stimuli. The small Red5 TPS family displays surprisingly high functional redundancy with five TPS producing linalool/nerolidol. Treatment of leaves and fruit with methyl jasmonate enhanced expression of a subset of defence-related TPS genes and stimulated the release of terpenes. Six TPS genes were induced upon herbivory of leaves by the economically important insect pest Ctenopseustis obliquana (brown-headed leaf roller) and emission, but not accumulation, of (E)- and (Z)-nerolidol was strongly linked to herbivory. Our results provide a framework to understand the overlapping biological and ecological roles of terpenes in Actinidia and other horticultural crops.

Waterlogging has occurred more frequently in recent years due to climate change, so it is a huge threat to crop yield and quality. Sweet cherry, a fruit tree with a high economic value, is sensitive to waterlogging stress. One of the most effective methods for enhancing the waterlogging tolerance of sweet cherries is to select waterlogging-tolerant rootstocks. However, the waterlogging tolerance of different cherry rootstocks, and the underlying mechanism remains uncharacterized. Thus, we first evaluated the waterlogging resistance of five sweet cherry rootstocks planted in China. The data showed that 'Gisela 12' and 'Colt' were the most waterlogging-sensitive and -tolerant among the five tested varieties, respectively. Oxygenation effectively alleviated the adverse impacts of waterlogging stress on cherry rootstocks. Moreover, we found that the waterlogging group had lower relative water content, Fv/Fm value, net photosynthetic rate, and higher antioxidant enzyme activities, whereas the oxygenated group performed better in all these parameters. RNA-Seq analysis revealed that numerous DEGs were involved in energy production, antioxidant metabolism, hormone metabolism pathways, and stress-related transcription factors. These findings will help provide management strategies to enhance the waterlogging tolerance of cherry rootstocks and thereby achieve higher yield and better quality of cherries.

The quantitative control of FLOWERING LOCUS T (FT) activation is important for the floral transition in flowering plants. However, the flowering regulation mechanisms in the day-neutral, summer-flowering chrysanthemum plant remain unclear. In this study, the chrysanthemum BBX7 homolog CmBBX7 was isolated and its flowering function was identified. The expression of CmBBX7 showed a diurnal rhythm and CmBBX7 exhibited higher expression levels than CmBBX8. Overexpression of CmBBX7 in transgenic chrysanthemum accelerated flowering, whereas lines transfected with a chimeric repressor (pSRDX-CmBBX7) exhibited delayed flowering. Yeast single hybridization, luciferase, electrophoretic mobility shift, and chromatin immunoprecipitation assays showed that CmBBX7 directly targets CmFTL1. In addition, we found that CmBBX7 and CmBBX8 interact to positively regulate the expression of CmFTL1 through binding to its promoter. Collectively, these results highlight CmBBX7 as a key cooperator in the BBX8-FT module to control chrysanthemum flowering.

The ribosomal protein contains complex structures that belong to polypeptide glycoprotein family, which are involved in plant growth and responses to various stresses. In this study, we found that capsicum annuum 40S ribosomal protein SA-like (CaSLP) was extensively accumulated in the cell nucleus and cell membrane, and the expression level of CaSLP was up-regulated by Salicylic acid (SA) and drought treatment. Significantly fewer peppers plants could withstand drought stress after CaSLP gene knockout. The transient expression of CaSLP leads to drought tolerance in pepper, and Arabidopsis's ability to withstand drought stress was greatly improved by overexpressing the CaSLP gene. Exogenous application of SA during spraying season enhanced drought tolerance. CaSLP-knockdown pepper plants demonstrated a decreased resistance of Pseudomonas syringae PV.tomato (Pst) DC3000 (Pst.DC3000), whereas ectopic expression of CaSLP increased the Pst.DC3000 stress resistance in Arabidopsis. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) results showed that CaNAC035 physically interacts with CaSLP in the cell nucleus. CaNAC035 was identified as an upstream partner of the CaPR1 promoter and activated transcription. Collectively the findings demonstrated that CaSLP plays an essential role in the regulation of drought and Pst.DC3000 stress resistance.

Although it is well established that nitrogen (N) deficiency induces leaf senescence, the molecular mechanism of N deficiency-induced leaf senescence remains largely unknown. Here, we show that an abscisic acid (ABA)-responsive NAC transcription factor (TF) is involved in N deficiency-induced leaf senescence. The overexpression of MdNAC4 led to increased ABA levels in apple calli by directly activating the transcription of the ABA biosynthesis gene MdNCED2. In addition, MdNAC4 overexpression promoted N deficiency-induced leaf senescence. Further investigation showed that MdNAC4 directly bound the promoter of the senescence-associated gene (SAG) MdSAG39 and upregulated its expression. Interestingly, the function of MdNAC4 in promoting N deficiency-induced leaf senescence was enhanced in the presence of ABA. Furthermore, we identified an interaction between the ABA receptor protein MdPYL4 and the MdNAC4 protein. Moreover, MdPYL4 showed a function similar to that of MdNAC4 in ABA-mediated N deficiency-induced leaf senescence. These findings suggest that ABA plays a central role in N deficiency-induced leaf senescence and that MdPYL4 interacts with MdNAC4 to enhance the response of the latter to N deficiency, thus promoting N deficiency-induced leaf senescence. In conclusion, our results provide new insight into how MdNAC4 regulates N deficiency-induced leaf senescence.

Actinidia eriantha is a characteristic fruit tree featuring with great potential for its abundant vitamin C and strong disease resistance. It has been used in a wide range of breeding programs and functional genomics studies. Previously published genome assemblies of A. eriantha are quite fragmented and not highly contiguous. Using multiple sequencing strategies, we get the haplotype-resolved and gap-free genomes of an elite breeding line "Midao 31" (MD), termed MDHAPA and MDHAPB. The new assemblies anchored to 29 pseudochromosome pairs with a length of 619.3 Mb and 611.7 Mb, as well as resolved 27 and 28 gap-close chromosomes in a telomere-to-telomere (T2T) manner. Based on the haplotype-resolved genome, we found that most alleles experienced purifying selection and coordinately expressed. Owing to the high continuity of assemblies, we defined the centromeric regions of A. eriantha, and identified the major repeating monomer, which is designated as Ae-CEN153. This resource lays a solid foundation for further functional genomics study and horticultural traits improvement in kiwifruit.