Yueying Sun

The bHLH (basic helix–loop–helix) transcription factors function as crucial regulators in numerous biological processes including abiotic stress responses and plant development. According to our RNA-seq analysis of tomato seedlings under salt stress, we found that, although the bHLH gene family in tomato has been studied, there are still so many tomato bHLH genes that have not been identified and named, which will hinder the later study of SlbHLHs. In total, 195 SlbHLHs that were unevenly distributed onto 12 chromosomes were identified from the tomato genome and were classified into 27 subfamilies based on their molecular features. The collinearity between SlbHLHs and interrelated orthologs from 10 plants further revealed evolutionary insights into SlbHLHs. Cis-element investigations of SlbHLHs promotors further suggested the potential roles of SlbHLHs in tomato development and stress responses. A total of 30 SlbHLHs were defined as the differentially expressed genes in response to salt stress by RNA-seq. The expression profiles of selected SlbHLHs were varyingly and markedly induced by multiple abiotic stresses and hormone treatments. These results provide valuable information to further understand the significance and intricacy of the bHLH transcription factor family, and lay a foundation for further exploring functions and possible regulatory mechanisms of SlbHLH members in abiotic stress tolerance, which will be significant for the study of tomato stress resistance and agricultural productivity.

The maintenance of the root stem cell niche identity in Arabidopsis relies on the delicate balance of reactive oxygen species (ROS) levels in root tips; however, the intricate molecular mechanisms governing ROS homeostasis within the root stem cell niche remain unclear. In this study, we unveil the role of ATP hydrolase superfamily protein 1 (ASP1) in orchestrating root stem cell niche maintenance through its interaction with the redox regulator cystathionine β-synthase domain-containing protein 3 (CBSX3). ASP1 is exclusively expressed in the quiescent center (QC) cells and governs the integrity of the root stem cell niche. Loss of ASP1 function leads to enhanced QC cell division and distal stem cell differentiation, attributable to reduced ROS levels and diminished expression of SCARECROW and SHORT ROOT in root tips. Our findings illuminate the pivotal role of ASP1 in regulating ROS signaling to maintain root stem cell niche homeostasis, achieved through direct interaction with CBSX3.

Expansins (EXPs) which are the essential components of plant cell wall function as relaxation factors to directly promote turgor-driven expansion of cell wall and control plant growth and development and diverse environmental stress responses. A lot of EXPs genes have been widely identified and characterized in numerous plant species, but not in sweetpotato. In the present study, a total of 59 EXPs genes that unevenly distributed onto 14 of 15 chromosomes were identified from sweetpotato genome, and segmental and tandem duplications were exhibited to act as dominant functions in IbEXPs diversity. Phylogenetic analysis exhibited that IbEXPs members were clustered into four subfamilies according to EXPs in Arabidopsis and rice and the regularity of motif, domain and gene structures was in accordance with the subfamily classification. The collinearity analysis between IbEXPs and related homologous sequences in 9 plants provided the phylogenetic insights of EXPs gene family. Cis-element analysis futhrer revealed the potential roles of IbEXPs in sweetpotato development and stress responses. Evidence from RNA-seq and qRT-PCR analysis of eight selected IbEXPs genes displayed their various tissue specificity in different tissues, and their transcripts were varyingly induced or suppressed under multiple hormone treatments (ABA, SA, JA and ACC) and abiotic stresses (low and high temperature). These results supply worthy foundations to further comprehensively investigate the exact functions of IbEXPs genes, and multiple members may function as promising regulators to control plant development and enhance the stress resistance of transgenic plants.