Drought and waterlogging seriously affect the growth of plants and are considered severe constraints on agricultural and forestry productivity; their frequency and degree have increased over time due to global climate change. The morphology, photosynthetic activity, antioxidant enzyme system and hormone levels of plants could change in response to water stress. The mechanisms of these changes are introduced in this review, along with research on key transcription factors and genes. Both drought and waterlogging stress similarly impact leaf morphology (such as wilting and crimping) and inhibit photosynthesis. The former affects the absorption and transportation mechanisms of plants, and the lack of water and nutrients inhibits the formation of chlorophyll, which leads to reduced photosynthetic capacity. Constitutive overexpression of 9-cis-epoxydioxygenase (NCED) and acetaldehyde dehydrogenase (ALDH), key enzymes in abscisic acid (ABA) biosynthesis, increases drought resistance. The latter forces leaf stomata to close in response to chemical signals, which are produced by the roots and transferred aboveground, affecting the absorption capacity of CO₂, and reducing photosynthetic substrates. The root system produces adventitious roots and forms aerenchymal to adapt the stresses. Ethylene (ETH) is the main response hormone of plants to waterlogging stress, and is a member of the ERFVII subfamily, which includes response factors involved in hypoxia-induced gene expression, and responds to energy expenditure through anaerobic respiration. There are two potential adaptation mechanisms of plants (“static” or “escape”) through ETH-mediated gibberellin (GA) dynamic equilibrium to waterlogging stress in the present studies. Plant signal transduction pathways, after receiving stress stimulus signals as well as the regulatory mechanism of the subsequent synthesis of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) enzymes to produce ethanol under a hypoxic environment caused by waterlogging, should be considered. This review provides a theoretical basis for plants to improve water stress tolerance and water-resistant breeding.

Multiprotein bridging factor 1 (MBF1) is a crucial transcriptional coactivator in animals, plants, and some microorganisms, that plays a necessary role in growth development and stress tolerance. Zanthoxylum armatum is an important perennial plant for the condiments and pharmaceutical industries, whereas the potential information in the genes related to stress resistance remains poorly understood in Z. armatum. Herein, six representative species were selected for use in a genome-wide investigation of the MBF1 family, including Arabidopsis thaliana, Oryza sativa, Populus trichocarpa, Citrus sinensis, Ginkgo biloba, and Z. armatum. The results showed that the MBF1 genes could be divided into two groups: Group I contained the MBF1a and MBF1b subfamilies, and group II was independent of the MBF1c subfamily.. Most species have at least two different MBF1 genes, and MBF1c is usually an essential member. The three ZaMBF1 genes were respectively located on ZaChr26, ZaChr32, and ZaChr4 of Zanthoxylum chromosomes. The collinearity were occurred between three ZaMBF1 genes, and ZaMBF1c showed the collinearity between Z. armatum and both P. trichocarpa and C. sinensis. Moreover, many cis-elements associated with abiotic stress and phytohormone pathways were detected in the promoter regions of MBF1 of six representative species. The ERF binding sites were the most abundant targets in the sequences of the ZaMBF1 family, and some transcription factor sites related to floral differentiation were also identified in ZaMBF1c, such as MADS, LFY, Dof, and AP2. ZaMBF1a was observed to be very highly expressed in 25 different samples except in the seeds, and ZaMBF1c may be associated with the male and female floral initiation processes. In addition, expression in all the ZaMBF1 genes could be significantly induced by water-logging, cold stress, ethephon, methyl jasmonate, and salicylic acid treatments, especially in ZaMBF1c. The present study carried out a comprehensive bioinformatic investigation related to the MBF1 family in six representative species, and the responsiveness of ZaMBF1 genes to various abiotic stresses and phytohormone inductions was also revealed. This work not only lays a solid foundation to uncover the biological roles of the ZaMBF1 family in Z. armatum, but also provides some broad references for conducting the MBF1 research in other plants.

Zanthoxylum armatum is a prominent plant for food industries. Its male flowers often occur in gynogenesis plants; however, the potential mechanism remains poorly understood. Herein, a total of 26 floral sex differentiation stages were observed to select four vital phases to reveal key factors by using RNA-seq, phytohormones and carbohydrates investigation. The results showed that a selective abortion of stamen or pistil primordia could result in the floral sex differentiation in Z. armatum. Carbohydrates might collaborate with cytokinin to effect the male floral differentiation, whereas female floral differentiation was involved in SA, GA₁, and ABA biosynthesis and signal transduction pathways. Meanwhile, these endogenous regulators associated with reproductive growth might be integrated into ABCDE model to regulate the floral organ differentiation in Z. armatum. Furthermore, the 21 crucial candidates were identified in co-expression network, which would contribute to uncovering their roles in floral sex differentiation of Z. armatum in further studies. To the best of our knowledge, this study was the first comprehensive investigation to link floral sex differentiation with multi-level endogenous regulatory factors in Z. armatum. It also provided new insights to explore the regulatory mechanism of floral sex differentiation, which would be benefited to cultivate high-yield varieties in Z. armatum.

Zanthoxylum armatum DC. is an economic tree species sensitive to waterlogging. Melatonin can improve the waterlogging tolerance of plants. In this study, we investigated the effects of different waterlogging times (including 0, 1, 2 and 3 d) and melatonin concentration (including 0, 400 and 800 μmol/L) on photosynthetic pigments, photosynthetic capabilities and chlorophyll fluorescence parameters of Z. armatum seedlings under waterlogging stress. Our results showed that waterlogging stress decreased the chlorophyll contents, photosynthetic rate (P_n), stomatal conductance (G_s), maximum efficiency of PSII photochemistry (F_v/F_m), quantum yield of PSII photochemistry (Y(II)), effective photochemical quantum yield of PSII (\({{F_{{\text{v}}}^{'}} \mathord{\left/ {\vphantom {{F_{{\text{v}}}^{'}} {F_{{\text{m}}}^{'}}}} \right. \kern-0em} {F_{{\text{m}}}^{'}}}\)), as well as efficiency of electron transfer (ETR) with the increase of waterlogging time. On the contrary, the intercellular CO₂ concentration (C_i), photochemical quenching (q_P) and nonphotochemical quenching coefficient (NPQ) increased under waterlogging stress. However, melatonin could mitigate waterlogging-induced reductions in photosynthetic capacity. Melatonin improved photosynthesis by enhancing the chlorophyll and carotenoid content and photosynthesis rate. In addition, melatonin promotes stomatal function, electron transport in PSII and photosynthesis efficiency. Melatonin had a concentration-dependent effect on Z. armatum seedlings under waterlogging stress, and the optimum concentration is 400 μmol/L. It indicated that exogenous melatonin application could effectively ameliorate the repression of photosynthesis caused by waterlogging, and thus enhance the seedling tolerance to waterlogging stress.

The walnut is an excellent food product with abundant nutrients. However, the inference of its population structure has been hindered by the intricate phylogenetic relationships among Juglans species. In this study, RAD sequencing was conducted to investigate the genetic variation and population structure among 41 walnut cultivars from Southwestern Sichuan (SS, n = 10), Eastern Sichuan (ES, n = 26) and Northern China (NC, n = 5). The resulting 6357 single-nucleotide polymorphisms divided the 41 walnut cultivars into two major groups corresponding to the ES and SS gene pools, and NC was clustered with the ES1 subgroup. Additionally, two cultivars, WB01 and SMJ, were reclassified to correct their previous morphological classifications. The migration rate from ES to SS was greater than that in the reverse direction, and the genetic differentiation between the ES and SS populations was high. Moreover, the estimated expected heterozygosity (H_e = 0.308) and polymorphism levels (P_i (π) = 0.030) of the SS group were greater than those of the ES group. Similarly, the average genetic distance of the SS population (0.563) was higher than that of the ES population (0.522), and the rate of linkage disequilibrium decay in the SS population was faster. All the results indicate that the SS population has greater genetic diversity and is more primitive than the ES group. The present study provides a theoretical basis for the division, conservation, and utilization of walnut germplasm resources, and these findings can be applied in breeding programs to obtain high-quality cultivars of Juglans.