TOPOISOMERASE1 (TOP1), which releases DNA torsional stress generated during replication through its DNA relaxation activity, plays vital roles in animal and plant development. In Arabidopsis (Arabidopsis thaliana), TOP1 is encoded by two paralogous genes (TOP1α and TOP1β), of which TOP1α displays specific developmental functions that are critical for the maintenance of shoot and floral stem cells. Here, we show that maintenance of two different populations of root stem cells is also dependent on TOP1α-specific developmental functions, which are exerted through two distinct novel mechanisms. In the proximal root meristem, the DNA relaxation activity of TOP1α is critical to ensure genome integrity and survival of stele stem cells (SSCs). Loss of TOP1α function triggers DNA double-strand breaks in S-phase SSCs and results in their death, which can be partially reversed by the replenishment of SSCs mediated by ETHYLENE RESPONSE FACTOR115. In the quiescent center and root cap meristem, TOP1α is epistatic to RETINOBLASTOMA-RELATED (RBR) in the maintenance of undifferentiated state and the number of columella stem cells (CSCs). Loss of TOP1α function in either wild-type or RBR RNAi plants leads to differentiation of CSCs, whereas overexpression of TOP1α mimics and further enhances the effect of RBR reduction that increases the number of CSCs. Taken together, these findings provide important mechanistic insights into understanding stem cell maintenance in plants.

Purpose: Although there have been numerous studies on single-incision laparoscopic inguinal hernia repair (SIL-IHR), the short- and long-term outcomes in patients from a large single institution who underwent single-incision laparoscopic transabdominal preperitoneal hernioplasty (SIL-TAPP) have rarely been reported. The purpose of this study is to evaluate the short- and long-term outcomes of SIL-TAPP and its safety and feasibility in patients from a large single institution. Methods: The details of 1,054 procedures in 966 patients who underwent SIL-TAPP at the Affiliated Hospital of Nantong University from January 2015 to October 2022 were retrospectively analysed. SIL-TAPP was performed completely through the umbilicus using conventional laparoscopic instruments. Short-term and long-term outcomes of SIL-TAPP were collected by outpatient and telephone follow-ups. In addition, we further compared the operation time, length of postoperative hospital stay, and postoperative complications of patients with simple and complicated unilateral inguinal hernias. Results: A total of 1,054 procedures were performed for 878 unilateral inguinal hernias and 88 bilateral inguinal hernias. In total, there were 803 (76.2%) indirect inguinal hernias, 192 (18.2%) direct inguinal hernias, 51 (4.8%) femoral hernias and 8 (0.8%) combined hernias. The mean operative time was 35.5 ± 17.0 min for unilateral inguinal hernias and 51.9 ± 25.5 min for bilateral inguinal hernias. There was one (0.1%) conversion to two-incision laparoscopic transabdominal preperitoneal hernioplasty. No intraoperative haemorrhages, inferior epigastric vessel injury or nerve damage occurred. Postoperative complications were minor and could be resolved without surgical intervention. The mean length of hospital stay was 1.3 ± 0.8 days. The median follow-up was 44 months, no trocar hernia occurred, and there was one (0.1%) recurrence. The operation time in the complicated inguinal hernia group was significantly higher than that in the simple inguinal hernia group (38.9 ± 22.3 vs. 35.0 ± 15.6, p = 0.025). The length of postoperative hospital stay and complication rate of the complicated inguinal hernia group were slightly higher than those of the simple inguinal hernia group, but the difference was not statistically significant. Conclusion: SIL-TAPP is safe and technically feasible, and both short- and long-term outcomes are acceptable.