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<jats:p>Autotoxicity is a key factor that leads to obstacles in continuous cropping systems. Although Si is known to improve plant resistance to biotic and abiotic stresses, little is known about its role in regulating leaf water status, mineral nutrients, nitrogen metabolism, and root morphology of cucumber under autotoxicity stress. Here, we used cucumber seeds (<jats:italic>Cucumis sativus</jats:italic> L. cv. “Xinchun No. 4”) to evaluate how exogenous Si (1 mmol L<jats:sup>−1</jats:sup>) affected the leaf water status, mineral nutrient uptake, N metabolism-related enzyme activities, root morphology, and shoot growth of cucumber seedlings under 0.8 mmol L<jats:sup>−1</jats:sup> CA-induced autotoxicity stress. We found that CA-induced autotoxicity significantly reduced the relative water content and water potential of leaves and increase their cell sap concentration. CA-induced stress also inhibited the absorption of major (N, P, K, Ca, Mg) and trace elements (Fe, Mn, Zn). However, exogenous Si significantly improved the leaf water status (relative water content and water potential) of cucumber leaves under CA-induced stress. Exogenous Si also promoted the absorption of mineral elements by seedlings under CA-induced stress and alleviated the CA-induced inhibition of N metabolism-related enzyme activities (including nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, glutamate dehydrogenase). Moreover, exogenous Si improved N uptake and utilization, promoted root morphogenesis, and increased the growth indexes of cucumber seedlings under CA-induced stress. Our findings have far-reaching implications for overcoming the obstacles to continuous cropping in cucumber cultivation.</jats:p>

<jats:p>Plant functional traits are a representation of plant resource utilization strategies. Plants with higher specific leaf area (SLA) and lower leaf dry matter content (LDMC) exhibit faster investment-return resource utilization strategies. However, the distribution patterns and driving factors of plant resource utilization strategies at the macroscale are rarely studied. We investigated the relative importance of climatic and soil factors in shaping plant resource utilization strategies at different life forms in forests using data collected from 926 plots across 163 forests in China. SLA and LDMC of plants at different life forms (i.e., trees, shrubs, and herbs) differ significantly. Resource utilization strategies show significant geographical differences, with vegetation in the western arid regions adopting a slower investment-return survival strategy and vegetation in warmer and wetter areas adopting a faster investment-return survival strategy. SLA decreases significantly with increased temperature and reduced rainfall, and vegetation growing in these conditions exhibits conservative resource utilization. Mean annual precipitation (MAP) is a key climatic factor that controls the resource utilization strategies of plants at the macroscale. Plants use resources more conservatively as soil pH increases. The influence of climate and soil factors is coupled to determine the resource utilization strategies of plants occupying different life forms at the macroscale, but the relative contribution of each varies across life forms. Our findings provide a theoretical framework for understanding the potential impact of increasing global temperatures on plant resource utilization.</jats:p>

<jats:p>Bud dormancy, which enables damage from cold temperatures to be avoided during winter and early spring, is an important adaptive mechanism of deciduous fruit trees to cope with seasonal environmental changes and temperate climates. Understanding the regulatory mechanism of bud break in fruit trees is highly important for the artificial control of bud break and the prevention of spring frost damage. However, the molecular mechanism underlying the involvement of MYB TFs during the bud break of peach is still unclear. In this study, we isolated and identified the <jats:italic>PpMYB52</jats:italic> (Prupe.5G240000.1) gene from peach; this gene is downregulated in the process of bud break, upregulated in response to ABA and downregulated in response to GA. Overexpression of <jats:italic>PpMYB52</jats:italic> suppresses the germination of transgenic tomato seeds. In addition, Y2H, Bimolecular fluorescence complementation (BiFC) assays verified that <jats:italic>PpMYB52</jats:italic> interacts with a RING-type E3 ubiquitin ligase, <jats:italic>PpMIEL1</jats:italic>, which is upregulated during bud break may positively regulate peach bud break by ubiquitination-mediated degradation of <jats:italic>PpMYB52</jats:italic>. Our findings are the first to characterize the molecular mechanisms underlying the involvement of MYB TFs in peach bud break, increasing awareness of dormancy-related molecules to avoid bud damage in perennial deciduous fruit trees.</jats:p>

<jats:p><jats:italic>Dendrobium officinale</jats:italic>, an important orchid plant with great horticultural and medicinal values, frequently suffers from abiotic or biotic stresses in the wild, which may influence its well-growth. Heat shock proteins (<jats:italic>Hsp</jats:italic>s) play essential roles in the abiotic stress response of plants. However, they have not been systematically investigated in <jats:italic>D. officinale</jats:italic>. Here, we identified 37 <jats:italic>Hsp20</jats:italic> genes (<jats:italic>DenHsp20</jats:italic>s), 43 <jats:italic>Hsp70</jats:italic> genes (<jats:italic>DenHsp70</jats:italic>s) and 4 <jats:italic>Hsp90</jats:italic> genes (<jats:italic>DenHsp90</jats:italic>s) in <jats:italic>D. officinale</jats:italic> genome. These genes were classified into 8, 4 and 2 subfamilies based on phylogenetic analysis and subcellular predication, respectively. Sequence analysis showed that the same subfamily members have relatively conserved gene structures and similar protein motifs. Moreover, we identified 33 pairs of paralogs containing 30 pairs of tandem duplicates and 3 pairs of segmental duplicates among these genes. There were 7 pairs in <jats:italic>DenHsp70</jats:italic>s under positive selection, which may have important functions in helping cells withstand extreme stress. Numerous gene promoter sequences contained stress and hormone response <jats:italic>cis</jats:italic>-elements, especially light and MeJA response elements. Under MeJA stress, <jats:italic>DenHsp20</jats:italic>s, <jats:italic>DenHsp70</jats:italic>s and <jats:italic>DenHsp90</jats:italic>s responded to varying degrees, among which <jats:italic>DenHsp20-5,6,7,16</jats:italic> extremely up-regulated, which may have a strong stress resistance. Therefore, these findings could provide useful information for evolutional and functional investigations of <jats:italic>Hsp20</jats:italic>, <jats:italic>Hsp70</jats:italic> and <jats:italic>Hsp90</jats:italic> genes in <jats:italic>D. officinale</jats:italic>.</jats:p>

<jats:p>Salt stress decreases plant growth and is a major threat to crop yields worldwide. The present study aimed to alleviate salt stress in plants by inoculation with halophilic plant growth-promoting rhizobacteria (PGPR) isolated from an extreme environment in the Qinghai–Tibetan Plateau. Wheat plants inoculated with <jats:italic>Bacillus halotolerans</jats:italic> KKD1 showed increased seedling morphological parameters and physiological indexes. The expression of wheat genes directly involved in plant growth was upregulated in the presence of KKD1, as shown by real-time quantitative PCR (RT-qPCR) analysis. The metabolism of phytohormones, such as 6-benzylaminopurine and gibberellic acid were also enhanced. Mining of the KKD1 genome corroborated its potential plant growth promotion (PGP) and biocontrol properties. Moreover, KKD1 was able to support plant growth under salt stress by inducing a stress response in wheat by modulating phytohormone levels, regulating lipid peroxidation, accumulating betaine, and excluding Na<jats:sup>+</jats:sup>. In addition, KKD1 positively affected the soil nitrogen content, soil phosphorus content and soil pH. Our findings indicated that KKD1 is a promising candidate for encouraging wheat plant growth under saline conditions.</jats:p>

<jats:p>As the core regulation network for the abscisic acid (ABA) signaling pathway, the PYL-PP2C-SnRK2s family commonly exists in many species. For this study, a total of 9 BsPYLs, 66 BsPP2Cs, and 7 BsSnRK2s genes were identified based on the genomic databases of <jats:italic>Bletilla striata</jats:italic>, which were classified into 3, 10, and 3 subgroups, respectively. Basic bioinformatics analysis completed, including the physicochemical properties of proteins, gene structures, protein motifs and conserved domains. Multiple <jats:italic>cis</jats:italic>-acting elements related to stress responses and plant growth were found in promoter regions. Further, 73 genes were localized on 16 pseudochromosomes and 29 pairs of paralogous genes were found via intraspecific collinearity analysis. Furthermore, tissue-specific expression was found in different tissues and germination stages. There were two <jats:italic>BsPYLs</jats:italic>, 10 <jats:italic>BsPP2Cs</jats:italic>, and four <jats:italic>BsSnRK2</jats:italic> genes that exhibited a difference in response to multiple abiotic stresses. Moreover, subcellular localization analysis revealed six important proteins BsPP2C22, BsPP2C38, BsPP2C64, BsPYL2, BsPYL8, and BsSnRK2.4 which were localized in the nucleus and plasma membrane. Finally, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays suggested that BsPP2C22 and BsPP2C38 could interact with multiple BsPYLs and BsSnRK2s proteins. This study systematically reported on the identification and characterization of the PYL-PP2C-SnRK2s family in <jats:italic>B. striata</jats:italic>, which provided a conceptual basis for deep insights into the functionality of ABA core signal pathways in Orchidaceae.</jats:p>

<jats:p>Plants employ an array of photoprotection mechanisms to alleviate the harmful effects of high light intensity. The violaxanthin cycle, which is associated with non-photochemical quenching (NPQ), involves violaxanthin de-epoxidase (VDE), and zeaxanthin epoxidase (ZEP) and is one of the most rapid and efficient mechanisms protecting plants under high light intensity. Woody bamboo is a class of economically and ecologically important evergreen grass species widely distributed in tropical and subtropical areas. However, the function of VDE in bamboo has not yet been elucidated. In this study, we found that high light intensity increased NPQ and stimulated the de-epoxidation of violaxanthin cycle components in moso bamboo (<jats:italic>Phyllostachys edulis</jats:italic>), whereas, samples treated with the VDE inhibitor (dithiothreitol) exhibited lower NPQ capacity, suggesting that violaxanthin cycle plays an important role in the photoprotection of bamboo. Further analysis showed that not only high light intensity but also extreme temperatures (4 and 42°C) and drought stress upregulated the expression of <jats:italic>PeVDE</jats:italic> in bamboo leaves, indicating that <jats:italic>PeVDE</jats:italic> is induced by multiple abiotic stresses. Overexpression of <jats:italic>PeVDE</jats:italic> under the control of the <jats:italic>CaMV 35S</jats:italic> promoter in <jats:italic>Arabidopsis</jats:italic> mutant <jats:italic>npq1</jats:italic> mutant could rescue its NPQ, indicating that <jats:italic>PeVDE</jats:italic> functions in dissipating the excess absorbed light energy as thermal energy in bamboo. Moreover, compared with wild-type (Col-0) plants, the transgenic plants overexpressing <jats:italic>PeVDE</jats:italic> displayed enhanced photoprotection ability, higher NPQ capacity, slower decline in the maximum quantum yield of photosystem II (<jats:italic>F</jats:italic><jats:sub><jats:italic>v</jats:italic></jats:sub>/<jats:italic>F</jats:italic><jats:sub><jats:italic>m</jats:italic></jats:sub>) under high light intensity, and faster recovery under optimal conditions. These results suggest that <jats:italic>PeVDE</jats:italic> positively regulates the response to high light intensity in bamboo plants growing in the natural environment, which could improve their photoprotection ability through the violaxanthin cycle and NPQ.</jats:p>

<jats:p>Co-inoculation of arbuscular mycorrhizal fungi (AMF) and bacteria can synergically and potentially increase nitrogen use efficiency (NUE) in plants, thus, reducing nitrogen (N) fertilizers use and their environmental impact. However, limited research is available on AMF-bacteria interaction, and the definition of synergisms or antagonistic effects is unexplored. In this study, we adopted a response surface methodology (RSM) to assess the optimal combination of AMF (<jats:italic>Rhizoglomus irregulare and Funneliformis mosseae</jats:italic>) and <jats:italic>Bacillus megaterium</jats:italic> (a PGPR—plant growth promoting rhizobacteria) formulations to maximize agronomical and chemical parameters linked to N utilization in maize (<jats:italic>Zea mays</jats:italic> L.). The fitted mathematical models, and also 3D response surface and contour plots, allowed us to determine the optimal AMF and bacterial doses, which are approximately accorded to 2.1 kg ha<jats:sup>–1</jats:sup> of both formulations. These levels provided the maximum values of SPAD, aspartate, and glutamate. On the contrary, agronomic parameters were not affected, except for the nitrogen harvest index (NHI), which was slightly affected (<jats:italic>p</jats:italic>-value of &amp;lt; 0.10) and indicated a higher N accumulation in grain following inoculation with 4.1 and 0.1 kg ha<jats:sup>–1</jats:sup> of AMF and <jats:italic>B. megaterium</jats:italic>, respectively. Nonetheless, the identification of the saddle points for asparagine and the tendency to differently allocate N when AMF or PGPR were used alone, pointed out the complexity of microorganism interaction and suggests the need for further investigations aimed at unraveling the mechanisms underlying this symbiosis.</jats:p>

<jats:p>N-Acetylserotonin O-methyltransferase (ASMT) is the final enzyme involved in melatonin biosynthesis. Identifying the expression of ASMT will reveal the regulatory role in the development and stress conditions in soybean. To identify and characterize ASMT in soybean (GmASMT), we employed genome-wide analysis, gene structure, cis-acting elements, gene expression, co-expression network analysis, and enzyme assay. We found seven pairs of segmental and tandem duplication pairs among the 44 identified GmASMTs by genome-wide analysis. Notably, co-expression network analysis reported that distinct GmASMTs are involved in various stress response. For example, GmASMT3, GmASMT44, GmASMT17, and GmASMT7 are involved in embryo development, heat, drought, aphid, and soybean cyst nematode infections, respectively. These distinct networks of GmASMTs were associated with transcription factors (NAC, MYB, WRKY, and ERF), stress signalling, isoflavone and secondary metabolites, calcium, and calmodulin proteins involved in stress regulation. Further, GmASMTs demonstrated auxin-like activities by regulating the genes involved in auxin transporter (WAT1 and NRT1/PTR) and auxin-responsive protein during developmental and biotic stress. The current study identified the key regulatory role of GmASMTs during development and stress. Hence GmASMT could be the primary target in genetic engineering for crop improvement under changing environmental conditions.</jats:p>

<jats:p>Subtropical tree species may experience severe drought stress due to variable rainfall under future climates. However, the capacity to restore hydraulic function post-drought might differ among co-occurring species with contrasting leaf habits (e.g., evergreen and deciduous) and have implications for future forest composition. Moreover, the links between hydraulic recovery and physiological and morphological traits related to water-carbon availability are still not well understood. Here, potted seedlings of six tree species (four evergreen and two deciduous) were grown outdoors under a rainout shelter. They grew under favorable water conditions until they were experimentally subjected to a soil water deficit leading to losses of <jats:italic>ca.</jats:italic> 50% of hydraulic conductivity, and then soils were re-watered to field capacity. Traits related to carbon and water relations were measured. There were differences in drought responses and recovery between species, but not as a function of evergreen or deciduous groups. <jats:italic>Sapindus mukorossi</jats:italic> exhibited the most rapid drought response, which was associated with a suite of physiological and morphological traits (larger plant size, the lowest hydraulic capacitance (<jats:italic>C</jats:italic><jats:sub>branch</jats:sub>), higher minimum conductance (<jats:italic>g</jats:italic><jats:sub>min</jats:sub>) and lower <jats:italic>HV</jats:italic> (Huber value)). Upon re-watering, xylem water potential exhibited fast recovery in 1–3 days among species, while photosynthesis at saturating light (<jats:italic>A</jats:italic><jats:sub>sat</jats:sub>) and stomatal conductance (<jats:italic>g</jats:italic><jats:sub>s</jats:sub>) recovery lagged behind water potential recovery depending on species, with <jats:italic>g</jats:italic><jats:sub>s</jats:sub> recovery being more delayed than <jats:italic>A</jats:italic><jats:sub>sat</jats:sub> in most species. Furthermore, none of the six species exhibited significant hydraulic recovery during the 7 days re-watering period, indicating that xylem refilling was apparently limited; in addition, NSC availability had a minimal role in facilitating hydraulic recovery during this short-term period. Collectively, if water supply is limited by insignificant hydraulic recovery post-drought, the observed carbon assimilation recovery of seedlings may not be sustained over the longer term, potentially altering seedling regeneration and shifting forest species composition in subtropical China under climate change.</jats:p>