Quercus fabri Hance, Quercus serrata Thunb, Quercus acutissima Carruth, and Quercus variabilis BL are four Chinese oak species commonly used for forestation. To ensure the survival of seedlings, we first need to understand the differences in drought resistance of the four oak species at the seedling stage, and comprehensively evaluate their drought resistance capabilities. The four oak seedlings were divided into drought-rewatering treatment group and well watered samples (control group). For the seedlings of the drought-rewatering treatment group, drought stress lasting 31 days was used, and then re-watering for 5 days. The water parameters, osmotic solutes content, antioxidant enzyme activity and photosynthesis parameters of the seedlings in the two groups were measured every 5 days. Compared with the control group, the relative water content, water potential, net photosynthetic rate, transpiration rate, and stomatal conductance levels of the four oaks all showed a downward trend under continuous drought stress, and showed an upward trend after rehydration. The soluble protein, soluble sugar, proline, peroxidase, superoxide dismutase and catalase content of the four oaks increased first and then decreased under drought stress, and then increased after rehydration. The content of glycine betaine and malondialdehyde continued to increase, and gradually decreased after rehydration. The weight of each index was calculated by principal component analysis, and then the comprehensive evaluation of each index was carried out through the membership function method. The drought resistance levels of the four oak species were as follows: Q. serrata > Q. fabri > Q. variabilis > Q. acutissima.

The APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors (TFs) are involved in the regulation of specialized terpenoids biosynthesis. However, the AP2/ERF TFs in the Litsea cubeba have not been characterized, and their role in the biosynthesis of terpenoids is unknown. Here, 174 LcAP2/ERF TFs were identified in L. cubeba and categorized into four subfamilies: 27 AP2, 7 RAV, 1 Soloist, and 139 ERF (I to Xb-L). Transcriptomic and qRT-PCR assays both showed that the expression levels of LcERF19 were similar to that of terpene synthase LcTPS42 in pericarp, which is related to the synthesis of geranial and neral in L. cubeba. LcERF19 was further identified to encode a nuclear-localized protein and was strongly induced at the transcriptomic level by jasmonate. Furthermore, a yeast one-hybrid and dual-luciferase experiment showed that LcERF19 bonded to the GCC box elements of the LcTPS42 promoter and promoted its activity. Transient overexpression of LcERF19 in L. cubeba and overexpression of LcERF19 in tomato both resulted in a significant increase in geranial and neral. Our findings show that LcERF19 enhances geranial and neral biosynthesis mightily through activation of LcTPS42 expression, which provides strategies to improve the flavor of tomato fruit and other crops’ fruit.

Analysis of genetic diversity and population structure among Quercus fabri populations is essential for the conservation and utilization of Q. fabri resources. Here, the genetic diversity and structure of 158 individuals from 13 natural populations of Quercus fabri in China were analyzed using genotyping‐by‐sequencing (GBS). A total of 459,564 high‐quality single nucleotide polymorphisms (SNPs) were obtained after filtration for subsequent analysis. Genetic structure analysis revealed that these individuals can be clustered into two groups and the structure can be explained mainly by the geographic barrier, showed gene introgression from coastal to inland areas and high mountains could significantly hinder the mutual introgression of genes. Genetic diversity analysis indicated that the individual differences within groups are greater than the differences between the two groups. These results will help us better understand the genetic backgrounds of Q. fabri.