Tansley, C. | bioRxiv Science

bioRxiv2022

CIPK-B is essential for salt stress signalling in Marchantia polymorpha

O_LICalcium signalling is central to many plant processes, with families of calcium decoder proteins having expanded across the green lineage and redundancy existing between decoders. The liverwort Marchantia polymorpha has fast become a new model plant, but it is unclear what calcium decoders exist in this species. C_LIO_LIWe have performed phylogenetic analyses to identify the Calcineurin B-Like (CBL) and CBL-Interacting Protein Kinase (CIPK) network of M. polymorpha. We analysed CBL-CIPK expression during salt stress, and determined protein-protein interactions using yeast two-hybrid and bimolecular fluorescence complementation. We also created genetic knockouts using CRISPR/Cas9. C_LIO_LIWe confirm that M. polymorpha has two CIPKs and three CBLs. Both CIPKs and only one CBL show salt-responsive transcriptional changes. All M. polymorpha CBL-CIPKs interact with each other in planta. Knocking out CIPK-B causes increased sensitivity to salt suggesting that this CIPK is involved in salt signalling. C_LIO_LIWe have identified CBL-CIPKs that form part of a salt tolerance pathway in M. polymorpha. Phylogeny and interaction studies imply that these CBL-CIPKs form an evolutionarily conserved Salt Overly Sensitive (SOS) pathway. Hence, salt responses may be some of the early functions of CBL-CIPK networks and increased abiotic stress tolerance required for land plant emergence. C_LI

plant biology↗

bioRxiv2022

Tunable control of insect pheromone biosynthesis in Nicotiana benthamiana

Previous work has demonstrated that plants can be used as production platforms for molecules used in health, medicine, and agriculture. Production has been exemplified in both stable transgenic plants and using transient expression strategies. In particular, species of Nicotiana have been engineered to produce a range of useful molecules, including insect sex pheromones, which are valued for species-specific control of agricultural pests. To date, most studies have relied on strong constitutive expression of all pathway genes. However, work in microbes has demonstrated that yields can be improved by controlling and balancing gene expression. Synthetic regulatory elements that provide control over the timing and levels of gene expression are therefore useful for maximizing yields from heterologous biosynthetic pathways. In this study, we demonstrate the use of pathway engineering and synthetic genetic elements for controlling the timing and levels of production of Lepidopteran sex pheromones in Nicotiana benthamiana. We demonstrate that copper can be used as a low-cost molecule for tightly regulated inducible expression. Further, we show how construct architecture influences relative gene expression and, consequently, product yields in multigene constructs. We compare a number of synthetic orthogonal regulatory elements and demonstrate maximal yields from constructs in which expression is mediated by dCas9-based synthetic transcriptional activators. The approaches demonstrated here provide new insights into the heterologous reconstruction of metabolic pathways in plants.

synthetic biology↗