Small RNA sequencing provides candidate miRNA-target pairs for revealing the mechanism of apomixis in Zanthoxylum bungeanum

Ultrasonic-assisted extraction of total flavonoids from Zanthoxylum bungeanum residue and their allelopathic mechanism on Microcystis aeruginosa

Water eutrophication has emerged as a pressing concern for massive algal blooms, and these harmful blooms can potentially generate harmful toxins, which can detrimentally impact the aquatic environment and human health. Consequently, it is imperative to identify a safe and efficient approach to combat algal blooms to safeguard the ecological safety of water. This study aimed to investigate the procedure for extracting total flavonoids from Z. bungeanum residue and assess its antioxidant properties. The most favorable parameters for extracting total flavonoids from Z. bungeanum residue were a liquid-solid ratio (LSR) of 20 mL/g, a solvent concentration of 60%, an extraction period of 55 min, and an ultrasonic temperature of 80 °C. Meanwhile, the photosynthetic inhibitory mechanism of Z. bungeanum residue extracts against M. aeruginosa was assessed with a particular focus on the concentration-dependent toxicity effect. Z. bungeanum residue extracts damaged the oxygen-evolving complex structure, influenced energy capture and distribution, and inhibited the electron transport of PSII in M. aeruginosa. Furthermore, the enhanced capacity for ROS detoxification enables treated cells to sustain their photosynthetic activity. The findings of this study hold considerable relevance for the ecological management community and offer potential avenues for the practical utilization of resources in controlling algal blooms.

Six Express Sequence Tag-Simple Sequence Repeat Primers Reveal Genetic Diversity in the Cultivars of Three Zanthoxylum Species

Zanthoxylum (Sichuan pepper), with its rich cultivars, has long been widely cultivated in China for its unique seasoning and medicinal uses, but most of its cultivars have similar morphological characteristics. Therefore, we hypothesized that the genetic diversity of Zanthoxylum cultivars is low because of their apomixis and long cultivation history. In this study, we aimed to investigate the genetic diversity of three Zanthoxylum species on the cultivar level based on express sequence tag-simple sequence repeat (EST-SSR) primers. In total, 121 samples of three Zanthoxylum species (Z. bungeanum, Z. armatum and Z. piperitum) were collected from different areas in China for genetic diversity analysis. A total of six specificity and polymorphism EST-SSR primers, which we selected from among 120 primers based on two transcriptomes (Z. bungeanum, Z. armatum) in our earlier study, were used to evaluate genetic diversity based on capillary electrophoresis technology. The results of our analysis using the unweighted pair group method with arithmetic mean (UPGMA) indicated that most of the samples are clustered in one clade in the UPGMA dendrogram, and the average genetic distance was 0.6409. Principal component analysis (PCA) showed that Z. piperitum may have a closer genetic relationship with Z. bungeanum than with Z. armatum. An analysis of molecular variation (AMOVA) showed that the genetic variation mainly stemmed from individuals within populations; the genetic differentiation coefficient (PhiPT) was 0.429, the gene flow (Nm) between populations was 0.333, and the differences among populations were not significant (p > 0.001). For the intraspecific populations of ZB, the percentage of genetic variation was 53% among populations and 47% within populations, with non-significant differences between populations (p > 0.001). The genetic differentiation coefficient (PhiT) was 0.529, and the gene flow (Nm) was 0.223. For the intraspecific populations of ZA, the results indicated that the percentage of genetic variation was 29% among populations and 71% within populations, with non-significant differences between populations (p > 0.001); the genetic differentiation coefficient (PhiPT) was 0.293, and the gene flow (Nm) was 0.223. Through genetic structure analysis (GSA), we predicted that these 121 samples belonged to two optimal subgroups, which means that all the samples probably originated from two gene pools. Above all, this indicated that the genetic diversity of the 121 Zanthoxylum samples was relatively low at both the species and cultivar levels, a finding which was consistent with our initial assumptions. This study provides a reference, with molecular-level data, for the further identification of Zanthoxylum species.

Apomixis: oh, what a tangled web we have!

Apomixis is a complex evolutionary trait with many possible origins. Here we discuss various clues and causes, ultimately proposing a model harmonizing the three working hypotheses on the topic. Asexual reproduction through seeds, i.e., apomixis, is the holy grail of plant biology. Its implementation in modern breeding could be a game-changer for agriculture. It has the potential to generate clonal crops and maintain valuable complex genotypes and their associated heterotic traits without inbreeding depression. The genetic basis and origins of apomixis are still unclear. There are three central hypothesis for the development of apomixis that could be: i) a deviation from the sexual developmental program caused by an asynchronous development, ii) environmentally triggered through epigenetic regulations (a polyphenism of sex), iii) relying on one or more genes/alleles. Because of the ever-increasing complexity of the topic, the path toward a detailed understanding of the mechanisms underlying apomixis remains unclear. Here, we discuss the most recent advances in the evolution perspective of this multifaceted trait. We incorporated our understanding of the effect of endogenous effectors, such as small RNAs, epigenetic regulation, hormonal pathways, protein turnover, and cell wall modification in response to an upside stress. This can be either endogenous (hybridization or polyploidization) or exogenous environmental stress, mainly due to oxidative stress and the corresponding ROS (Reacting Oxygen Species) effectors. Finally, we graphically represented this tangled web.

Integrated microRNA and transcriptome profiling reveals the regulatory network of embryo abortion in jujube

Hybridization is an important approach to the production of new varieties with exceptional traits. Although the kernel rate of wild jujube (Ziziphus jujuba Mill. var. spinosa Hu.) is generally high, that of cultivated jujube (Z. jujuba Mill.) is low, greatly hampering the jujube breeding process. However, the mechanism by which this trait changed during jujube domestication remains unclear. Here, we explored the potential regulatory network that governs jujube embryo abortion using correlation analysis of population traits, artificial pollination, sugar content measurements and multi-omics analysis. The results showed that embryo abortion was an important reason for the low kernel rate of cultivated jujube, and kernel rate was negatively correlated with edible rate. Twenty-one days after pollination was a critical period for embryo abortion. At this time, the sugar content of cultivated 'Junzao' kernels decreased significantly compared with that of the pulp, but sugar content remained relatively stable in kernels of wild 'Suanzao'. A total of 1142 differentially expressed genes targeted by 93 microRNAs (miRNAs) were identified by transcriptome, miRNA and degradome sequencing, and may be involved in the regulation of embryo abortion during kernel development. Among them, DELLA protein, TCP14 and bHLH93 transcription factors have been shown to participate in the regulation of embryonic development. Our findings suggest that carbohydrate flow between different tissues of cultivated jujube exhibits a bias toward the pulp at 21 days after pollination, thereby restricting the process of kernel development. This information enhances our understanding of the embryo abortion process and reveals miRNA-target gene pairs that may be useful for molecular-assisted breeding.

A combined transcriptome - miRNAome approach revealed that a kinesin gene is differentially targeted by a novel miRNA in an apomictic genotype of Eragrostis curvula

Weeping lovegrass (Eragrostis curvula [Shrad.] Nees) is a perennial grass typically established in semi-arid regions, with good adaptability to dry conditions and sandy soils. This polymorphic complex includes both sexual and apomictic cytotypes, with different ploidy levels (2x-8x). Diploids are known to be sexual, while most polyploids are facultative apomicts, and full apomicts have also been reported. Plant breeding studies throughout the years have focused on achieving the introgression of apomixis into species of agricultural relevance, but, given the complexity of the trait, a deeper understanding of the molecular basis of regulatory mechanisms of apomixis is still required. Apomixis is thought to be associated with silencing or disruption of the sexual pathway, and studies have shown it is influenced by epigenetic mechanisms. In a previous study, we explored the role of miRNA-mRNA interactions using two contrasting E. curvula phenotypes. Here, the sexual OTA-S, the facultative Don Walter and the obligate apomictic Tanganyika cDNA and sRNA libraries were inquired, searching for miRNA discovery and miRNA expression regulation of genes related to the reproductive mode. This allowed for the characterization of seven miRNAs and the validation of their miRNA-target interactions. Interestingly, a kinesin gene was found to be repressed in the apomictic cultivar Tanganyika, targeted by a novel miRNA that was found to be overexpressed in this genotype, suggestive of an involvement in the reproductive mode expression. Our work provided additional evidence of the contribution of the epigenetic regulation of the apomictic pathway.