Homologs of Larix kaempferiDEFICIENS-AGAMOUS-LIKE 1 (LaDAL1) promote flowering in Arabidopsis. However, their functional role in the whole life-cycle is limited. Here, we analyzed the phenotypes and transcriptomes of Arabidopsis plants over-expressing LaDAL1. With respect to the defined life-cycle stage of Arabidopsis based on the meristem state, the results showed that LaDAL1 promoted seed germination, bolting, flower initiation, and global proliferative arrest, indicating that LaDAL1 accelerates the meristem reactivation, the transitions of vegetative meristem to inflorescence and flower meristem, and meristem arrest. As a marker gene of meristem, TERMINAL FLOWER 1 was down-regulated after LaDAL1 over-expression. These results reveal that LaDAL1 accelerates the life-cycle progression in Arabidopsis by promoting the transition of meristem fate, providing more and novel functional information about the conifer age-related gene DAL1.

Perennial woody plants are long-lived, and their life-cycle events occur in order in each generation, but what drives the occurrence and restart of these events in their offspring is unknown. Based on its age-dependent expression pattern and function, Larix kaempferi DEFICIENS-AGAMOUS-LIKE 1 (LaDAL1), a MADS transcription factor has been suggested to be a time recorder and life-cycle event coordinator. Here, we studied the dynamic spatiotemporal expression pattern of LaDAL1 in the life cycle of L. kaempferi to analyze the molecular mechanism of life-cycle progression. In full view of the life cycle, LaDAL1 transcription was related with life-cycle progression, and its transcript level increased sharply from age 3 to 5 years, which might be the molecular characteristic of the vegetative phase change, and then stayed at a high level. During sexual reproduction, LaDAL1 transcript level decreased sequentially during meiosis and embryogenesis, suggesting that meiosis rapidly lowers the age signal, and after fertilization, the age signal was reset to “0” with the embryogenesis. When a seed germinates, the next generation restarts, and the age is re-counted. Altogether, these results not only provide important and novel insights into the life-cycle progression and transgeneration in perennial woody plants, but also advance our understanding of age recording.

Somatic embryogenesis is valuable for clonal propagation and genetic improvement, and it also serves as an ideal system for studying plant development mechanisms. In Larix kaempferi, microRNA171 and its target gene L. kaempferi SCARECROW-LIKE6 (LaSCL6), which has two alternative splicing variants, can regulate somatic embryogenesis; however, the underlying molecular mechanism is still unknown. In this study, we overexpressed these two LaSCL6 variants in Oryza sativa and Arabidopsis thaliana and then used the RNA-Seq method to screen genes from O. sativa and A. thaliana, whose expression patterns are related to those of LaSCL6 variants. The screened genes were then used to search L. kaempferi proteins to identify the candidate target genes of LaSCL6. After yeast one-hybrid and dual- luciferase transcriptional activity assays, cytochrome P450, family 89, subfamily A, polypeptide 5 (CYP89A5), and wall-associated receptor kinase-like 20 (WAKL20) were confirmed to be the target genes of LaSCL6-var1; in addition, WAKL20 and UDP-glycosyltransferase 85A3 (UGT85A3) were confirmed to be the target genes of LaSCL6-var2. Moreover, APETALA2-like protein 2, a transcription factor from the AP2/ERF family, was shown to interact with LaSCL6-var1 and LaSCL6-var2. Taken together, our results suggest a regulatory network of miR171-LaSCL6. The findings presented here not only provide novel insights into the regulation of the miR171-LaSCL6 module but also explain the mechanism underlying larch somatic embryogenesis and other biological processes.

As one of the most important vegetables globally, peppers have garnered significant attention from breeders due to their diverse agronomic traits, including plant type, leaf shape, and maturity. Understanding the genetic mechanisms underlying these traits is crucial for systematic advancements in sweet pepper breeding. In this study, leveraging the PepperSNP50K liquid breeding chip, we conducted a comprehensive analysis of horticultural traits and genetic diversity using sweet pepper germplasm samples. Initially, the sweet pepper populations were analyzed using SNP-based liquid chip technology. Subsequently, phenotypic surveys were performed on 217 sweet pepper samples, and the collected phenotypic data were integrated with SNP markers to conduct a genome-wide association study (GWAS) of key agronomic traits. Among the 25 horticultural traits evaluated, 11 exhibited significant associations with 54 SNP polymerization regions and 193 candidate genes. These findings provide a robust foundation for the utilization of sweet pepper germplasm resources and the development of new, improved varieties. Furthermore, in this study, we identified Caz06g05770 (Lycopene beta-cyclase) as a candidate gene responsible for the color of mature ripe fruits. This research not only enhances our understanding of the genetic basis of sweet pepper traits but also offers a practical roadmap for advancing breeding programs and boosting agricultural productivity. By bridging the gap between genetic research and practical breeding applications, this study paves the way for the development of high-yield, high-quality sweet pepper varieties tailored to meet the growing demands of global agriculture.

SCARECROW-LIKE6 (SCL6) plays a role in the formation and maintenance of the meristem. In Larix kaempferi (Lamb.) Carr., an important afforestation tree species in China, SCL6 (LaSCL6) has two alternative splicing variants—LaSCL6-var1 and LaSCL6-var2—which are regulated by microRNA171. However, their roles are still unclear. In this study, LaSCL6-var1 and LaSCL6-var2 were transformed into the Arabidopsis thaliana (L.) Heynh. genome, and the phenotypic characteristics of transgenic A. thaliana, including the germination percentage, root length, bolting time, flower and silique formation times, inflorescence axis length, and branch and silique numbers, were analyzed to reveal their functions. It was found that LaSCL6-var1 and LaSCL6-var2 overexpression shortened the root length by 41% and 31%, respectively, and increased the inflorescence axis length. Compared with the wild type, the bolting time in transgenic plants was delayed by approximately 2–3 days, the first flower and silique formation times were delayed by approximately 3–4 days, and the last flower and silique formation times were delayed by about 5 days. Overall, the life cycle in transgenic plants was prolonged by approximately 5 days. These results show that LaSCL6 overexpression inhibited the transitions from the vegetative meristem to inflorescence meristem and from the flower meristem to meristem arrest in A. thaliana, revealing the roles of LaSCL6-var1 and LaSCL6-var2 in the fate transition and maintenance of the meristem.

As an auxin-responsive gene, Gretchen Hagen 3 (GH3) maintains hormonal homeostasis by conjugating excess auxin with amino acids in plant stress-related signaling pathways. GH3 genes have been characterized in many plant species, but the characteristics of pepper (Capsicum annuum L.) GH3 (CaGH3) gene family members in response to multiple stimulants are largely unknown. In this study, we systematically identified the CaGH3 gene family at the genome level and identified eight members on four chromosomes in pepper. CaGH3s were divided into two groups (I and III) and shared conserved motifs, domains, and gene structures. Moreover, CaGH3s had close evolutionary relationships with tomato (Solanum lycopersicum L.), and the promoters of most CaGH3 genes contained hormone and abiotic stress response elements. A protein interaction prediction analysis demonstrated that the CaGH3-3/3-6/3-7/3-8 proteins were possibly core members of the CaGH3 family interaction. In addition, qRT-PCR results showed that CaGH3 genes were differentially expressed in pepper tissues and could be induced by phytohormones (IAA, ABA, and MeJA) and abiotic stresses (salt, low temperature, and drought) with different patterns. In addition, CaGH3-5 and CaGH3-7 were cloned, and the sequences showed a high degree of conservation. Moreover, the results of subcellular localization indicated that they were located in the membrane and chloroplast. Notably, after overexpressing CaGH3-7 in tomato, RNA-seq was performed on wild-type and transgenic lines, and the differentially expressed genes were mainly enriched in response to external stimuli. This study not only lays the foundation for a comprehensive understanding of the function of the CaGH3 gene family during plant growth and stress responses but also provides potential genetic resources for pepper resistance breeding.