Species pool size alters species‐area relationships during experimental community assembly
The species pool concept has advanced our understanding for how biodiversity is coupled at local and regional scales. However, it remains unclear how species pool size — the number of species available to disperse to a site — influences community assembly across spatial scales. Catano et al. provide one of the first studies that assesses diversity across scales after experimentally assembling grassland communities from species pools of different sizes. They show that species pool size causes scale‐dependent effects on diversity in grasslands undergoing restoration by altering the shape of the species‐area relationship (SAR). Specifically, larger species pools increased the slope of the SAR, but not the intercept, suggesting that dispersal from a larger pool causes species to be more spatially aggregated.
Ethylene-independent functions of the ethylene precursor ACC in Marchantia polymorpha
The plant hormone ethylene has many roles in growth and development. In seed plants, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is converted into ethylene by ACC oxidase (ACO), and treatment with ACC induces ethylene responses. However, non-seed plants lack ACO homologues. which led Li et al. to examine the relationship between ACC and ethylene in the liverwort Marchantia polymorpha. They demonstrate that ACC and ethylene can induce divergent growth responses in Marchantia.
[REDUX] Phosphatidylcholines from Pieris brassicae eggs activate an immune response in Arabidopsis
Recognition of conserved microbial molecules activates immune responses in plants, a process termed pattern-triggered immunity (PTI). Similarly, insect eggs trigger defences that impede egg development or attract predators, but information on the nature of egg-associated elicitors is scarce. Stahl et al. performed an unbiased bioactivity-guided fractionation of eggs of the butterfly Pieris brassicae. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry of active fractions led to the identification of phosphatidylcholines (PCs). PCs are released from insect eggs, and they induce salicylic acid and H2O2 accumulation, defense gene expression and cell death in Arabidopsis, all of which constitute a hallmark of PTI.
A heat-shock inducible system for flexible gene expression in cereals
Harrington et al. present an irreversible heat-shock inducible system developed using Golden Gate-compatible components which utilises Cre recombinase to drive constitutive gene expression in barley and wheat. They show that a heat shock treatment of 38 °C is sufficient to activate the construct and drive expression of the gene of interest. Modulating the duration of heat shock controls the density of induced cells. Short durations of heat shock cause activation of the construct in isolated single cells, while longer durations lead to global construct activation.
Condensation of Rubisco into a proto-pyrenoid in higher plant chloroplasts
Atkinson et al. show that expression of mature EPYC1 and a plant-algal hybrid Rubisco leads to spontaneous condensation of Rubisco into a single phase-separated compartment in Arabidopsis chloroplasts, with liquid-like properties similar to a pyrenoid matrix. The condensate displaces the thylakoid membranes and is enriched in hybrid Rubisco containing the algal Rubisco small subunit required for phase separation. Promisingly, photosynthetic CO2 fixation and growth is not impaired in stable transformants compared to azygous segregants. These observations represent a significant initial step towards enhancing photosynthesis in higher plants by introducing an algal CO2-concentrating mechanism, which is predicted to significantly increase the efficiency of photosynthetic CO2 uptake.
Ethylene signaling mediates host invasion by parasitic plants
Parasitic plants form a specialized organ, a haustorium, to invade host tissues and acquire water and nutrients. To understand the molecular mechanism of haustorium development, Cui et al. performed a forward genetics screening to isolate mutants exhibiting haustorial defects in the model parasitic plant Phtheirospermum japonicum. They isolated two mutants that show prolonged and sometimes aberrant meristematic activity in the haustorium apex, resulting in severe defects on host invasion.
What are the Top 10 Unanswered Questions in Molecular Plant-Microbe Interactions?
The past few decades have seen major discoveries in the field of molecular plant-microbe interactions. As the result of technological and intellectual advances, we are now able to answer questions at a level of mechanistic detail that we could not have imagined possible 20 years ago. The MPMI Editorial Board felt it was time to take stock and reassess. What big questions remain unanswered?
Molecular Plant-Microbe Interactions®
Receptor kinase module targets PIN-dependent auxin transport during canalization
Auxin signals travel through pathways in developing or regenerating plant tissues to guide tissue formation. Hajný et al. now show that an auxin-regulated receptor in turn regulates phosphorylation and thus subcellular localization of an auxin transporter. Through this signaling pathway, auxin builds the pathways through which it is transported, guiding development as it goes.
Comparative transcriptomic analysis reveals conserved transcriptional programs underpinning organogenesis and reproduction in land plants
The evolution of plant organs, including leaves, stems, roots, and flowers, mediated the explosive radiation of land plants, which shaped the biosphere and allowed the establishment of terrestrial animal life. Furthermore, the fertilization products of angiosperms, seeds serve as the basis for most of our food. The evolution of organs and immobile gametes required the coordinated acquisition of novel gene functions, the co-option of existing genes, and the development of novel regulatory programs. However, our knowledge of these events is limited, as no large-scale analyses of genomic and transcriptomic data have been performed for land plants. To remedy this, Julca et al. have generated gene expression atlases for various organs and gametes of 10 plant species comprising bryophytes, vascular plants, gymnosperms, and flowering plants. Comparative analysis of the atlases identified hundreds of organ- and gamete-specific gene families and revealed that most of the specific transcriptomes are significantly conserved. Interestingly, the appearance of organ-specific gene families does not coincide with the corresponding organ's appearance, suggesting that co-option of existing genes is the main mechanism for evolving new organs.
Effects of Nutrient and Water Supply During Fruit Development on Metabolite Composition in Tomato Fruits (Solanum lycopersicum L.) Grown in Magnesium Excess Soils
Tomato cultivation in the greenhouse or field may experience high surplus salts, including magnesium (Mg2+), which may result in differences in the growth and metabolite composition of fruits. This study hypothesized that decreasing the supply of nutrients and/or water would enhance tomato fruit quality in soils with excess Mg2+ that are frequently encountered in the field and aimed to find better supply conditions.Frontiers in Plant Science