A C4 plant K+ channel accelerates stomata to enhance C3 photosynthesis and water use efficiency.

Accelerating stomatal kinetics through synthetic optogenetics and mutations that enhance guard cell K+ flux has proven a viable strategy to improve water use efficiency and biomass production. Stomata of the model C4 species Gynandropsis gynandra, a relative of the C3 plant Arabidopsis thaliana, are similarly fast to open and close. We identified and cloned the guard cell rectifying outward K+ channel (GROK) of Gynandropsis and showed that GROK is preferentially expressed in stomatal guard cells.

Interaction Dynamics of Plant-Specific Insert Domains from : A Study of Homo- and Heterodimer Formation.

Plant aspartic proteinases (APs) from feature unique plant-specific insert (PSI) domains, which serve as essential vacuolar sorting determinants, mediating the transport of proteins to the vacuole. Although their role in vacuolar trafficking is well established, the exact molecular mechanisms that regulate PSI interactions and functions remain largely unknown. This study explores the ability of PSI A and PSI B to form homo- and heterodimers using a combination of pull-down assays, the mating-based split-ubiquitin system (mbSUS), and FRET-FLIM analyses.

Speedy stomata of a C plant correlate with enhanced K channel gating.

Stomata are microscopic pores at the surface of plant leaves that facilitate gaseous diffusion to support photosynthesis. The guard cells around each stoma regulate the pore aperture. Plants that carry out C photosynthesis are usually more resilient than C plants to stress, and their stomata operate over a lower dynamic range of CO within the leaf.

The K/HDEL receptor does not recycle but instead acts as a Golgi-gatekeeper.

Accurately measuring the ability of the K/HDEL receptor (ERD2) to retain the ER cargo Amy-HDEL has questioned earlier results on which the popular receptor recycling model is based upon. Here we demonstrate that ERD2 Golgi-retention, rather than fast ER export supports its function. Ligand-induced ERD2 redistribution is only observed when the C-terminus is masked or mutated, compromising the signal that prevents Golgi-to-ER transport of the receptor.

Engineering a K channel 'sensory antenna' enhances stomatal kinetics, water use efficiency and photosynthesis.

Stomata of plant leaves open to enable CO entry for photosynthesis and close to reduce water loss via transpiration. Compared with photosynthesis, stomata respond slowly to fluctuating light, reducing assimilation and water use efficiency. Efficiency gains are possible without a cost to photosynthesis if stomatal kinetics can be accelerated.

Synergy among Exocyst and SNARE Interactions Identifies a Functional Hierarchy in Secretion during Vegetative Growth.

Vesicle exocytosis underpins signaling and development in plants and is vital for cell expansion. Vesicle tethering and fusion are thought to occur sequentially, with tethering mediated by the exocyst and fusion driven by assembly of soluble NSF attachment protein receptor (SNARE) proteins from the vesicle membrane (R-SNAREs or vesicle-associated membrane proteins [VAMPs]) and the target membrane (Q-SNAREs). Interactions between exocyst and SNARE protein complexes are known, but their functional consequences remain largely unexplored.

Dual Sites for SEC11 on the SNARE SYP121 Implicate a Binding Exchange during Secretory Traffic.

SNARE (soluble -ethylmaleimide-sensitive factor attachment protein receptor) proteins facilitate vesicle traffic through their assembly in a heteromeric complex that drives membrane fusion. Much of vesicle traffic at the Arabidopsis () plasma membrane is subject to the Sec1/Munc18 protein SEC11, which, along with plasma membrane K channels, selectively binds with the SNARE SYP121 to regulate its assembly in complex. How SEC11 binding is coordinated with the K channels is poorly understood, as both SEC11 and the channels are thought to compete for the same SNARE binding site.

Predominant Golgi Residency of the Plant K/HDEL Receptor Is Essential for Its Function in Mediating ER Retention.

Accumulation of soluble proteins in the endoplasmic reticulum (ER) of plants is mediated by a receptor termed ER RETENTION DEFECTIVE2 (ERD2) or K/HDEL receptor. Using two gain-of-function assays and by complementing loss of function in , we discovered that compromising the lumenal N terminus or the cytosolic C terminus with fluorescent fusions abolishes its biological function and profoundly affects its subcellular localization. Based on the confirmed asymmetrical topology of ERD2, we engineered a new fluorescent ERD2 fusion protein that retains biological activity.