Environmental stresses, including abiotic and biotic stresses, have complex and diverse effects on the growth and development of woody plants, which have become a matter of contention due to concerns about the outcomes of climate change on plant resources, genetic diversity, and world food safety. Plant basic helix–loop–helix (bHLH) transcription factors (TFs) are involved in a variety of physiological processes and play an important role in biotic and abiotic stress responses of woody plants. In recent years, an increasing body of studies have been conducted on the bHLH TFs in woody plants, and the roles of bHLH TFs in response to various stresses are increasingly clear and precise. Therefore, it is necessary to conduct a systematic and comprehensive review of the progress of the research of woody plants. In this review, the structural characteristics, research history and roles in the plant growth process of bHLH TFs are summarized, the gene families of bHLH TFs in woody plants are summarized, and the roles of bHLH TFs in biotic and abiotic stresses in woody plants are highlighted. Numerous studies mentioned in this review have shown that bHLH transcription factors play a crucial role in the response of woody plants to biotic and abiotic stresses. This review serves as a reference for further studies about enhancing the stress resistance and breeding of woody plants. Also, the future possible research directions of bHLH TFs in response to various stresses in woody plants will be discussed.

Low-cadmium (Cd) accumulating wheat cultivars (LAWC-Cds) can effectively reduce the total Cd content in wheat grains (Grain-Cd). Thirteen LAWC-Cds were planted in three fields to study the enrichment, transport, and accumulation patterns of Cd in LAWC-Cds. Compared with the soil properties before planting, the soil pH and the total Cd content in the soil decreased, while the Cd content in the diethylenetriaminepentaacetic acid extract, soil conductivity, and soil organic matter increased at wheat maturity. The Cd enrichment capacity of the different organs of wheat decreased in the following order: root > leaf > rachis > stem > glume > grain. The dynamics of Cd accumulation in roots affected Grain-Cd, and these factors were negatively correlated. The Cd content and Cd accumulation in all organs of LAWC-Cds showed strong negative correlations with the lengths of the first and second internodes and highly significant positive correlations with both grains per spike and awn length. Structural equation modeling showed that the Cd content of wheat organs had the most direct effect (0.639) in determining Grain-Cd, and soil properties had the largest effect (0.744) in influencing Grain-Cd. This study is important for screening wheat cultivars with stable low Cd-accumulation characteristics.

MicroRNAs (miRNAs) represent the most abundant class of small RNAs in plants, in which the miR159 family demonstrates a high degree of conservation across various plant species and plays a crucial role in regulating anther, silique, and seed development by targeting GAMYB-like. The members of the Fan-miR159 family in cultivated strawberry target not only GAMYB-like genes but also Auxin Response Factor (ARF) family members, which are annotated as “ARF23-like” in the genome. In this study, we firstly analyzed the structural features, evolutionary conservation, and expression patterns of the miR159 family in Fragaria × ananassa. Then, we reannotated the “ARF23-like” genes in cultivated strawberry and found that they actually belong to the “ARF2b” subfamily. Finally, we utilized RT-qPCR and co-transformation experiments to analyze and validate our observation. The results showed the suppression of FaARF2b-2 expression by fan-miR159n and fan-miR159r in both tobacco and strawberry. Moreover, two transcripts of the FaARF2b-2 gene were detected in cultivated strawberry, FaARF2b-2R and FaARF2b-2M. The expression levels of both FaARF2b-2M and FaARF2b-2R increased following the abscisic acid (ABA) treatment, indicating that they may be positively regulated by ABA. In addition, FaARF2b-2M exhibits significantly higher expression levels in the anther compared to FaARF2b-2R, which potentially plays an important role in the male reproductive development. Our findings enhance the understanding of the miR159 family in cultivated strawberry and expand the knowledge regarding its novel targets.