Search for: All records

Somatic embryogenesis (SE) is a process by which an embryo is derived from somatic tissue. Transcription factors (TFs) have been identified that control this process. One such TF that promotes SE is AGAMOUS‐like 15 (AGL15). Prior work has shown that AGL15 can both induce and repress gene expression. One way this type of dual function TF works is via protein interactions, so a yeast 2‐hybrid (Y2H) screen was undertaken. One intriguing protein with which AGL15 interacted in Y2H was LBD40. LBD40 encodes a LATERAL ORGAN BOUNDARIES (LOB)‐domain TF that is unique to plants and is primarily expressed during seed development. Here, we confirm the AGL15‐LBD40 interaction by quantitative assays andin plantaco‐immunoprecipation. We also document a role for LBD40, and the closely related protein LBD41, in supporting SE. To determine downstream genes potentially controlled by LBD40, chromatin immunoprecipitation followed by high throughput sequencing (ChIP‐seq) was used. More than 400 binding regions for LBD40 were consistently found genome‐wide. To determine genes responsive to LBD40/41 accumulation, RNA‐seq analysis of transcriptomes of wild‐type control and loss‐of‐functionlbd40/lbd41was performed. Combining these datasets provides insight into genes directly and indirectly controlled by these LOB domain TFs. The gene ontology (GO) enrichment analysis of these regulated genes showed an overrepresentation of biological processes that are associated with SE, further indicating the importance of LBD40 in SE. This work provides insight into SE, a poorly understood, but essential process to generate transgenic plants to meet agricultural demands or test gene function. This manuscript reports on experiments to understand the role that LDB40, a TF, plays in support of SE by investigating genes directly and indirectly controlled by LBD40 and examining physical and genetic interactions with other TFs active in SE. We uncover targets of LBD40 and an interacting TF of the MADS family and investigate targets involvement in SE.

AGAMOUS-Like 18 (AGL18) is a MADS domain transcription factor (TF) that is structurally related to AGL15. Here we show that, like AGL15, AGL18 can promote somatic embryogenesis (SE) when ectopically expressed in Arabidopsis (Arabidopsis thaliana). Based on loss-of-function mutants, AGL15 and AGL18 have redundant functions in developmental processes such as SE. To understand the nature of this redundancy, we undertook a number of studies to look at the interaction between these factors. We studied the genome-wide direct targets of AGL18 to characterize its roles at the molecular level using chromatin immunoprecipitation (ChIP)-SEQ combined with RNA-SEQ. The results demonstrated that AGL18 binds to thousands of sites in the genome. Comparison of ChIP-SEQ data for AGL15 and AGL18 revealed substantial numbers of genes bound by both AGL15 and AGL18, but there were also differences. Gene ontology analysis revealed that target genes were enriched for seed, embryo, and reproductive development as well as hormone and stress responses. The results also demonstrated that AGL15 and AGL18 interact in a complex regulatory loop, where AGL15 inhibited transcript accumulation of AGL18, while AGL18 increased AGL15 transcript accumulation. Co-immunoprecipitation revealed an interaction between AGL18 and AGL15 in somatic embryo tissue. The binding and expression analyses revealed a complex crosstalk and interactions among embryo TFs and their target genes. In addition, our study also revealed that phosphorylation of AGL18 and AGL15 was crucial for the promotion of SE.

Alternative polyadenylation (APA) regulates diverse developmental and physiological processes through its effects on gene expression, mRNA stability, translatability, and transport.Sorghumis a major cereal crop in the world and, despite its importance, not much is known about the role of post‐transcriptional regulation in mediating responses to abiotic stresses inSorghum. A genome‐wide APA analysis unveiled widespread occurrence of APA inSorghumin response to drought, heat, and salt stress. Abiotic stress treatments incited changes in poly(A) site choice in a large number of genes. Interestingly, abiotic stresses led to the re‐directing of transcriptional output into non‐productive pathways defined by the class of poly(A) site utilized. This result revealed APA to be part of a larger global response ofSorghumto abiotic stresses that involves the re‐direction of transcriptional output into non‐productive transcriptional and translational pathways. Large numbers of stress‐inducible poly(A) sites could not be linked with known, annotated genes, suggestive of the existence of numerous unidentified genes whose expression is strongly regulated by abiotic stresses. Furthermore, we uncovered a novel stress‐specificcis‐element in intronic poly(A) sites used in drought‐ and heat‐stressed plants that might play an important role in non‐canonical poly(A) site choice in response to abiotic stresses.