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WOX11/12 is a homeobox gene of WOX11 and WOX12 in Arabidopsis that plays important roles in crown root development and growth. It has been reported that WOX11/12 participates in adventitious root (AR) formation and different abiotic stress responses, but the downstream regulatory network of WOX11/12 in poplar remains to be further investigated. In this study, we found that PagWOX11/12a is strongly induced by PEG-simulated drought stress. PagWOX11/12a -overexpressing poplar plantlets showed lower oxidative damage levels, greater antioxidant enzyme activities and reactive oxygen species (ROS) scavenging capacity than non-transgenic poplar plants, whereas PagWOX11/12a dominant repression weakened root biomass accumulation and drought tolerance in poplar. RNA-seq analysis revealed that several differentially expressed genes (DEGs) regulated by PagWOX11/12a are involved in redox metabolism and drought stress response. We used RT-qPCR and yeast one-hybrid (Y1H) assays to validate the downstream target genes of PagWOX11/12a. These results provide new insights into the biological function and molecular regulatory mechanism of WOX11/12 in the abiotic resistance processes of poplar. • PagWOX11/12a is induced by PEG-simulated drought stress. • Overexpression of PagWOX11/12a enhances drought tolerance by regulating ROS levels and antioxidant enzyme activity. • PagWOX11/12a can bind to the PagBURP24 and PagbHLH63 promoters and activate their expression. [ABSTRACT FROM AUTHOR]

NAC transcription factors play a significant role in regulating plant responses to biological processes and environmental stresses. Our previous study revealed 21 ThNAC proteins, and ThNAC13 is a nuclear protein that responds to saline stress in Tamarix hispida. To determine whether ThNAC13 regulates downstream genes, RNA sequencing (RNA-seq) and DNA affinity purification sequencing (DAP-seq) were used to identify the binding sites of ThNAC13 at the whole-genome level. In RNAi-silenced ThNAC13 transgenic Tamarix , a total of 4 downregulated differentially expressed genes (DEGs) and 114 peaks strongly associated with four different motifs were identified compared with those in empty vector transgenic Tamarix under salt stress. The c48149.graph_c0 gene contains the key domain of the phloem protein 2 (PP2) protein and is a candidate gene downstream of ThNAC13. Yeast one-hybrid (Y1H), chromatin immunoprecipitation (ChIP) and dual-luciferase reporter (LUC) assays were used to identify ThNAC13 as an upstream regulator of ThPP2. Transgenic Tamarix plants in which ThPP2 was transiently expressed or silenced via RNAi were used for functional gain and loss experiments. The ThPP2- overexpressing plants exhibited decreased hydrogen peroxide (H 2 O 2), superoxide (O 2 •−), and electrolyte leakage (EL) and malondialdehyde (MDA) levels and increased superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity. In contrast, transient RNAi-mediated silencing of ThPP2 in Tamarix had the opposite effect. ThNAC13 binds to the promoter region of the ThPP2 gene and reduces the reactive oxygen species (ROS) accumulation and enhances antioxidant enzyme activity, positively regulating salt stress tolerance in Tamarix. • 4 down-regulated DEGs and 4 different motifs were identified in RNAi-silenced ThNAC13 compare with empty vector transgenic Tamarix under salt stress. • The phloem protein 2 (PP2) protein as a downstream gene by ThNAC13 TFs. • Overexpression of ThPP2 Tamarix decreased the contents of H 2 O 2 , O 2 •−, EL and MDA; induced the activities of SOD, POD and CAT. • In contrast, transiently RNAi-silenced ThPP2 Tamarix showed the opposite result. • ThNAC13 binds to ThPP2 gene through reduces the ROS accumulation and enhances antioxidant enzyme activity to improve salt stress tolerance. [ABSTRACT FROM AUTHOR]

Adventitious root (AR) development is an extremely complex biological process that is affected by many intrinsic factors and extrinsic stimuli. Some WUSCHEL-related homeobox (WOX) transcription factors have been reported to play important roles in AR development, but their functional relationships with auxin signaling are poorly understood, especially the developmental plasticity of roots in response to adversity stress. Here, we identified that the WOX11/12a– SMALL AUXIN UP RNA36 (SAUR36) module mediates AR development through the auxin pathway in poplar, as well as under salt stress. PagWOX11/12a displayed inducible expression during AR development, and overexpression of PagWOX11/12a significantly promoted AR development and increased salt tolerance in poplar, whereas dominant repression of PagWOX11/12a produced the opposite phenotype. PagWOX11/12a proteins directly bind to the SAUR36 promoter to regulate SAUR36 transcription, and this binding was enhanced during salt stress. Genetic modification of PagWOX11/12a–PagSAUR36 expression revealed that the PagWOX11/12a –PagSAUR36 module is crucial for controlling AR development via the auxin pathway. Overall, our results indicate that a novel WOX11 –SAUR –auxin signaling regulatory module is required for AR development in poplar. These findings provide key insights and a better understanding of the involvement of WOX11 in root developmental plasticity in saline environments. [ABSTRACT FROM AUTHOR]

Tamarix taklamakanensis M. T. Liu is a perennial shrub that is highly tolerant to drought and can be used as an ideal material for investigating the molecular mechanisms of drought resistance. Here, we revealed the response of T. taklamakanensis to drought stress and rehydration treatment through physiological, transcriptomic and metabolic analyses. T. taklamakanensis seedlings were subjected to 0 (D0), 7 (D7) and 14 (D14) days of progressive drought stress followed by rewatering for 10 days (R10). These results indicated that drought stress influenced the plant phenotypic characteristics, physiological traits and enzyme activities. A total of 1618, 2716 and 485 differentially expressed genes (DEGs) in D7/D0, D14/D0 and R10/D0 were identified. These DEGs were involved in tryptophan and α-linolenic acid metabolism, flavonoid and phenylpropanoid biosynthesis and the mitogen-activated protein kinase (MAPK) signaling pathway. The contents of lipids and organic acids increased under drought for 7 days. Most alkaloids, amino acids and their derivatives, lignans and coumarins were increased under drought for 14 days and rewatering for 10 days. T. taklamakanensis responds to drought conditions by regulating the cutin, suberine and wax biosynthesis, the flavonoid pathway and α-linolenic acid metabolism, and responds to rewatering conditions by regulating the flavonoid pathway and α-linolenic acid metabolism, which provides reference data for further understanding the regulatory mechanism of drought tolerance in Tamarix. • A total of 1618, 2716 and 485DEGs were identified in D7/D0, D14/D0 and R10/D0. • RNA-seq and metabolome analysis of Tamarix under drought and rewatering conditions. • Many DEGs and DAMs involved in flavonoid and α-linolenic acid metabolism pathways. [ABSTRACT FROM AUTHOR]