Jiehua Wang

Tension wood (TW), a type of reaction wood that develops in angiosperm trees in response to gravistimulation, serves as an ideal model for investigating the regulatory mechanisms underlying xylem cell differentiation and cell wall deposition. The initial biological signals that induce the formation of reaction wood in response to gravitational stimuli remain poorly understood. In this study, we utilized pharmacological and genetic approaches to modulate Ca ²⁺ levels in hybrid white poplar ( Populus alba × P . glandulosa ) and examine the role of calcium signaling during the early stages of gravitropic responses. Our findings revealed differential cytosolic Ca ²⁺ signal distribution in gravistimulated stems during the early phase of gravity induction, characterized by lower Ca ²⁺ levels on the upper side (where TW forms) and higher Ca ²⁺ levels on the lower side (where opposite wood forms). Consistent with this hypothesis, plants treated with LaCl ₃ and those with genetically disrupted calcium channels ( PagGLR3.3 knockout using the CRISPR/Cas9 system) showed reduced Ca ²⁺ signals and developed characteristic TW features. These results suggest that decreased Ca ²⁺ levels induce the formation of TW. Furthermore, PagGLR3.3 knockout plants with TW‐like stems displayed diminished sensitivity to gravistimulation. Transcriptomic analysis revealed that the knockout of PagGLR3.3 resulted in the upregulation of genes associated with TW formation and reactive oxygen species (ROS) production. Notably, superoxide anion (O ₂ ^·− ) levels were significantly elevated in the cambium zone of stems subjected to gravistimulation, LaCl ₃ treatment, or PagGLR3.3 knockout, indicating that reduced Ca ²⁺ levels promote TW formation through increased O ₂ ^·− accumulation. This study offers novel insights into the critical role of Ca ²⁺ in gravitropism and TW induction in poplar.

Somatic embryogenesis receptor kinases (SERKs) are pivotal regulators of plant development and stress adaptation, known to integrate multiple signaling pathways, including brassinosteroid (BR)‐mediated responses to coordinately modulate stress‐related gene expression. While SERKs participate in biotic/abiotic stress regulation, their roles in heavy metal (HM) stress responses and BR‐mediated transcriptional control under HM exposure remain unexplored. Therefore, we systematically identified 20 BraSERK genes in Chinese cabbage ( Brassica rapa subsp. Pekinensis), revealing conserved domain architectures and stress‐responsive expression patterns. Three BraSERK members ( BraSERK9 , 12 , and 17 ) exhibited significant induction under Cd/Zn stress. The potential regulatory roles of BR on Chinese cabbage exposed to Cd/Zn stress were investigated in this study by exogenous spraying of 24‐epibrassinolide (EBR). The results showed that EBR could significantly increase total chlorophyll content, reduce Zn/Cd translocation, increase antioxidant capacity, and thus attenuate Cd/Zn‐induced toxicity. Moreover, EBR dynamically regulated BraSERKs expression in a tissue‐ and metal‐specific manner, potentiating BraSERK12/17 induction in Zn‐stressed shoots while suppressing BraSERK9 . Our findings suggest that BraSERKs may contribute to BR‐mediated HM adaptation, while EBR appears to play a dual protective role through both direct phytoprotection and potential modulation of SERK pathway activity under Cd/Zn co‐stress conditions. This study advances our understanding of BR‐mediated metal tolerance in crops, offering potential strategies to mitigate HM toxicity through targeted SERK pathway modulation.

Main conclusion Carbon nanotubes concentration modulates endogenous hormone balance, influencing callogenesis and organogenesis efficiency, with potential for optimizing plant transformation programs. Abstract A unique feature of plant somatic cells is their remarkable ability to regenerate new organs and even an entire plant in vitro. In this work, we investigated how an important group of environmental factors, carbon nanotubes (CNTs) (both single-walled nanotubes as SWCNTs and multi-walled nanotubes as MWCNTs), affect the regenerative capacity of plants and the underlying molecular mechanisms. Our data show that both the induction of pluripotent callus from Arabidopsis root explants and the frequency of de novo shoot regeneration were influenced by the concentration, but not the type of CNTs. Raman analyses show that CNTs can be transported and accumulate in the callus tissue and in the newly formed seedlings. The contrasting effects of CNTs at 0.1 mg L⁻¹ and 50 mg L⁻¹ were reflected not only in the concentrations of endogenous auxin and trans-zeatin (tZT), but also in the changes in the expression levels of positive cell cycle regulators and transcriptional regulators that control callus pluripotency and the establishment of shoot apical meristem (SAM). Since most existing plant transformation strategies involve the conversion of dedifferentiated calli into regenerated plantlets and are very time consuming and inefficient, this work suggests that CNTs could be used as an additive to optimize plant micropropagation and genetic engineering systems by modulating hormone balance and stimulating the intrinsic totipotency of plants, thus overcoming organogenic recalcitrance.