Insect resistance is an inherent characteristic of plants and determined by genotypic differences across plants. In this study, we determined differences in the gene expression patterns between two clones of Populus section Aigeiros after insect infestation and elucidated the mechanism of resistance induced by insect feeding. We performed differential gene expression (DEG) analysis by using Illumina Hiseq 2000 high-throughput sequencing of leaf samples from the upper, middle, and lower parts of Populus euramericana cv. ‘Neva’ (“P107”) and P. deltoids ‘Chuangxin’ (“P17-2”) infested with the insect. We selected 3,462 DEGs through a comparison between “P107” and “P17-2” (A vs. B). Based on the gene ontology analysis, the identified DEGs were functionally annotated, which revealed 20, 23, and 22 functional categories of “biological process”, “cellular component”, and “molecular function”, with enrichment mainly in “cellular process”, “cell part”, and “binding functions”, respectively. After insect feeding, the damaged leaves of “P107” and “P17-2” showed different degrees of resistance, along with upregulated defense gene expressions, reduced nutrient accumulation and photosynthesis, and enhanced secondary metabolite biosynthesis. This study provides a molecular basis for understanding the mechanism underlying insect resistance in plants.

Fitting mathematical models to describe the influence of topographic factors and coexisting plants on wild jujube distribution was performed to provide a scientific basis for wild jujube forestation. Investigation quadrats, with straight-line distances between adjacent quadrats of longer than 100 m, were set up in areas of wilderness or low human disturbance, which were rich in wild plant species. Data concerning altitude, slope aspect, slope position and slope degree of each investigation quadrat, as well as the type and number of coexisting wild plants, were collected. Based on this, correlations with the average number, occurrence probability and density of wild jujube and these variables were analyzed, and data models were established. Results of analyses show that topographic factors such as altitude, aspect, gradient, slope and position, play an important role in the distribution of wild jujube; and that Vitex negundo var. heterophylla (Franch.) Rehd. coexistence is related to wild jujube distribution. Both average number and occurrence probability of wild jujube conform to a GaussAmp model with altitude. The highest average number was recorded at 581.24 ± 13.78 m above sea level, and the highest occurrence probability at 462.53 ± 36.67 m above sea level. Average number and occurrence probability of wild jujube were fit to a linear model with slope aspect—with mathematical slope 0.49 ± 0.16—indicating that wild jujube is a light-loving and drought-tolerant plant. Average number and density of wild jujubes were fit to GaussAmp models with slope position. The highest average number and the highest density of wild jujube appears on the upper part of the middle slope. Wild jujube occurrence probability was correlated to slope degree in a quadratic equation model. With an increase in slope degree, the distribution number of wild jujube increased sharply. The survey data of slope position and slope degree further reinforced the observed drought-resistance qualities of wild jujube. Average number and density of wild jujubes were correlated to the number of Vitex negundo var. heterophylla by quadratic equation models. No other plants investigated conformed to a statistically significant relationship with wild jujube distribution. Our results suggest altitude, slope aspect, slope position and slope degree play an important role in wild jujube distribution, and that Vitex negundo var. heterophylla is an important coexistent plant species for wild jujube.

The tender leaves of Ziziphus jujuba var. spinosa (sour jujube) are widely consumed in China as a health-promoting tea, with triterpenoids being identified as one of their core bioactive constituents. However, key genes in the triterpenoid biosynthesis pathway remain largely uncharacterized in this species. Here, adenosine triphosphate (ATP) treatment inhibited sour jujube seedling growth, induced leaf curling and marginal withering in partial seedlings, and elevated triterpenoid content in seedling aboveground tissues. Transcriptome analysis showed that most mevalonic acid (MVA) pathway enzyme genes were not significantly altered, while some were downregulated, and some enzyme isoforms were slightly upregulated. Combined genome and transcriptome analysis identified one slightly upregulated oxidosqualene cyclase (OSC) gene, ZsLUS, among 13 sour jujube OSC family genes. Heterologous expression in yeast confirmed that ZsLUS encodes a bona fide lupeol synthase with catalytic activity. These results indicate that ATP treatment enhances triterpenoid accumulation without uniformly upregulating MVA pathway genes, suggesting a sub-pathway-specific regulatory mode or post-transcriptional regulatory mechanism for triterpenoid biosynthesis in sour jujube seedlings. This work deepens our understanding of the mechanism of ATP action on sour jujube triterpenoid biosynthesis and provides new clues for deciphering triterpenoid biosynthesis and accumulation in sour jujube leaves.