During their lifetime, plants encounter numerous biotic and abiotic stresses with diverse modes of attack. Phytohormones, including salicylic acid (SA), ethylene (ET), jasmonate (JA), abscisic acid ...(ABA), auxin (AUX), brassinosteroid (BR), gibberellic acid (GA), cytokinin (CK) and the recently identified strigolactones (SLs), orchestrate effective defense responses by activating defense gene expression. Genetic analysis of the model plant
has advanced our understanding of the function of these hormones. The SA- and ET/JA-mediated signaling pathways were thought to be the backbone of plant immune responses against biotic invaders, whereas ABA, auxin, BR, GA, CK and SL were considered to be involved in the plant immune response through modulating the SA-ET/JA signaling pathways. In general, the SA-mediated defense response plays a central role in local and systemic-acquired resistance (SAR) against biotrophic pathogens, such as Pseudomonas syringae, which colonize between the host cells by producing nutrient-absorbing structures while keeping the host alive. The ET/JA-mediated response contributes to the defense against necrotrophic pathogens, such as
, which invade and kill hosts to extract their nutrients. Increasing evidence indicates that the SA- and ET/JA-mediated defense response pathways are mutually antagonistic.
In seed plants, the ovule is the precursor to the seed. The process of ovule development and differentiation is regulated by multiple factors, including starch metabolism and endogenous hormones. ...Castanea henryi produces nuts with high nutritional value. However, the high proportion of empty buds restricts the commercial use of the tree. Previous studies have shown that the empty bud phenotype is closely related to ovule abortion. If none of the ovules in the ovary expand rapidly and develop in 7-8 weeks after pollination, an empty bud will form. Therefore, we studied the development and molecular mechanisms underlying single seed formation in C. henryi.
We found that 49 days after pollination (DAP) is a critical period for the formation of fertile and abortive ovules. The morphology and starch distribution of the fertile and abortive ovules differed significantly at 49 DAP. The fertile ovules were smooth and round in appearance, with a large amount of starch. In contrast, abortive ovules were smaller with only a small amount of starch. The embryo sac of the abortive ovule proceeded to develop abnormally, and the entire ovule lacked starch. We identified 37 candidate genes involved in metabolism with potential roles in the regulation of starch levels. Three ADP-glucose pyrophosphorylase (AGPase) genes, one granule-bound starch synthase (GBSS) gene, and two beta-amylase genes could affect starch accumulation. The levels of auxin, cytokinins, gibberellins, and jasmonic acid in fertile ovules were higher than those in abortive ovules. In addition, the levels of endogenous abscisic acid and salicylic acid in abortive ovules were higher than those in fertile ovules of the same age, consistent with the expression patterns of genes related to the synthesis of abscisic and salicylic acid and signal transduction. We identified and mapped the differentially expressed genes associated with hormone synthesis and signal transduction.
These results improve our general understanding of the molecular mechanisms underlying single seed development in C. henryi and the phenomenon of empty buds, providing directions for future research.
Castanea henryi
is a monoecious woody food tree species whose yield and industrialization potential are limited by its low female-to-male flower ratio. Here, the male flowers on the male ...inflorescence of
C. henryi
were converted to female flowers by triple applications of exogenous cytokinin (CK) (N-(2-chloro-4-pyridyl)-N’-phenylurea, CPPU). To study the role of exogenous CK in flower sex determination, cytological and transcriptomic analyses were performed on samples from the five stages after CK treatment. Cytological analysis showed that stage 3 (nine days after the last CK treatment) was the critical stage in the differential development of the pistil primordium and stamen primordium. On this basis, one key module and two modules with significant positive correlations with stage 3 were identified by weighted gene co-expression network analysis (WGCNA), combined with transcriptome data. The CK and GA biosynthesis- and signaling-related genes, three transcription factor (TF) families, and 11 floral organ identity genes were identified in the related modules. In particular, the TFs
WRKY47
,
ERF021
, and
MYB4
, and floral organ identity genes
AGL11
/
15
,
DEF
, and
SEP1
with large differences are considered to be critical regulators of sex determination in
C. henryi
. Based on these results, a genetic regulatory network for exogenous CK in the sex determination of flowers in
C. henryi
is proposed. This study contributes to the understanding of the role of CK in the sex regulation of flowers and provides new insights into the regulatory network of sex determination in
C. henryi.
To produce antioxidant substances from agricultural waste Camellia spp. fruit shells before their further utilization, gallic acid from five kinds of Camellia spp. fruit shells was separated on ...specific recognition by deep eutectic solvent molecularly imprinted polymers (DES@MIPs), which were prepared by bulk polymerization using gallic acid as the template and deep eutectic solvents (α-methylacrylic acid and choline chloride) as functional monomers. The optimized DES@MIPs were characterized by scanning electron microscopy, particle size analysis, nitrogen sorption porosimetry, elemental analysis, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. The adsorptive behavior of gallic acid on DES@MIPs was also investigated. The results indicated that DES@MIPs were successfully prepared as mesoporous materials with average pore diameter of 9.65 nm and total pore volume of 0.315 cm3 g−1, and the adsorption behavior was multilayer adsorption and pseudo-second-order kinetics with the saturation adsorptive capacity of gallic acid reaching 0.7110 mmol g−1. Although the content of gallic acid in five fruit shells was quite different, the purification recovery of gallic acid was high, ranging from 87.85–96.75% with a purity over 80%. Thus, the purification of gallic acid from Camellia spp. fruit shells could be realized feasibly using DES@MIPs with favorable economic and environmental benefits.
Oil-tea (
Camellia oleifera
) is an important woody plant species producing edible oil in southern China, which shows complicated cytogenetics and intraspecific polyploidy. In order to explore the ...ploidy variation in interspecific hybridization of oil-tea
Camellia
, the ploidy of ‘Huashuo’, ‘Youza 2’ and 18 superior hybrids of ‘Youza 2’ × ‘Huashuo’ were identified by flow cytometry and chromosome counting.
C.oleifera
variety ‘Huashuo’ was hexaploid (2
n
= 90), and
Camellia yuhsienensis
superior plant ‘Youza 2’ was aneuploid based on hexaploid (2
n
= 91). There are not only hexaploid but also aneuploid in the ‘Huashuo’ × ‘Youza 2’ hybrids. Among the offspring plants, there are 11 plants each with chromosome number of 90, 6 plants each with 91, and 1 plants each with 92. To elucidate the causes of ploidy variation in above findings, the pollen characteristics and chromosomal behavior in meiosis of ‘Huashuo’ were examined by microscopy. The chromosome pairing configuration of meiosis terminal stage of microsporocytes of ‘Huashuo’ was 43 II + 2 IV. In all stages of meiosis, numerous abnormal behaviors were found, such as precocious chromosome migration, free chromosomes, lagging chromosomes and micronucleus. The abnormal rates of metaphase I, anaphase I, metaphase II and anaphase II were 67.5%, 88.1%, 58.4% and 78.9%, respectively. In the tetrad stage, abnormal phenomena such as dyads, triads, hexads and micronucleus were observed, with the frequency of 1.4%, 1.0%, 1.0% and 4.2%, respectively. The pollen diameter of ‘Huashuo’ varied widely (16.92–79.13 μm), suggesting a wide range of ploidy level of pollen grains. From pollen diameter distribution, we concluded that ‘Huashuo’ produced a small number of unreduced pollen grains. These findings are valuable for cytogenetics research and selection strategy of ploidy breeding in
C. oleifera
.
The ovule is the most important reproductive organ in the pistil of phanerogamae. Camellia oleifera (Theaceae) is an important woody plant producing edible oil in southern China, and its embryo sac ...structure has a positive effect on seed breeding. In this study, the microstructure, ultrastructure and three‐dimensional structure of the ovule and embryo sac of C. oleifera were observed and described based on a combination of advanced microscopy techniques (SEM, TEM, CLSM). The ovule comprises the inner and outer integument. Large quantities of secretions in the micropylar canal exit and may participate in the guidance of the entry of the pollen tube into the embryo sac. The synergids have a dense cytoplasm, abundant organelles, and strong polarity. Little cytoplasm is present in the egg cell, yet there are many vacuoles. The center of the cell is taken up by a large vacuole, and the cytoplasm is pushed towards the edges to form obvious cytoplasmic cords. The two polar nuclei are large and conspicuous. The antipodal cells degenerate to fulfill a nutritional function.
Abel. (
) is an important woody edible oil tree species in China. The quality of
oil (tea oil) is mainly determined by the contents of linoleic acid (LA) and α-linolenic acid (ALA). However, how to ...increase the contents of LA and ALA in tea oil and the corresponding regulating mechanism have not been clarified. In the present study, we found that the LA and ALA contents in
seeds were significant positively associated with the concentrations of ethephon and were decreased by ethylene inhibitor treatment. Furthermore, 1.5 g L
ethephon could receive an optimal LA and ALA contents without adverse effects to the growth of 'Huashuo' trees in this study. The ethephon treatment also increased the contents of 1-aminocyclopropane-1-carboxylic acid (ACC), sucrose, soluble sugar and reducing sugar contents in seeds. Transcriptome analysis further suggested that exogenous ethephon application enhanced the accumulation of LA and ALA
regulating genes involved in LA and ALA metabolism, plant hormone signal transduction pathways, and starch and sucrose metabolism. Our findings confirm the role of ethylene in LA and ALA regulation and provide new insights into the potential utilization of ethylene as a LA and ALA inducer in
cultivation.
Chinquapin (
Castanea henryi
) is a dual-purpose tree species in China valued for as a source of timber and starch. We investigated the effect of four cutting mediums (pure vermiculite; peat:river ...sand at 3:1 v/v; peat:krasnozem at 1:1 v/v; and pure krasnozem) and three stem cutting periods (March, May, and July) on rooting performance of
C. henryi
cuttings. Different cutting periods and cutting mediums greatly influenced the rooting rate of
C. henryi
, ranging from 3.35 to 77.31%. Principal component analysis indicated that the best combination of cutting period and cutting medium was semi-hardwood cuttings (May cuttings) + krasnozem. Histological evidence indicated that adventitious root initials were present by week 5–6, and that the site of root primordia initiation was observed in the vascular cambium. Stem anatomical structures observed at different periods indicated that a xylem/radius ratio of 29.90–37.42% and a fractured phloem fiber ring are indicative of rooting success. The relational model between rooting index and medium properties indicated that nutrient content and porosity significantly influenced callus production. However, pH strongly affected
C. henryi
root formation, with the Pearson correlation coefficients for May and July cuttings of − 0.856 and − 0.947, respectively. Our protocol is helpful to achieve mass clone propagation of improved
C. henryi
genotypes, thus overcoming a common hurdle in chinquapin breeding programs.
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