Codevelopment of the lungs and heart underlies key evolutionary innovations in the transition to terrestrial life. Cardiac specializations that support pulmonary circulation, including the atrial septum, are generated by second heart field (SHF) cardiopulmonary progenitors (CPPs). It has been presumed that transcription factors required in the SHF for cardiac septation, e.g., Tbx5, directly drive a cardiac morphogenesis gene-regulatory network. Here, we report instead that TBX5 directly drives Wnt ligands to initiate a bidirectional signaling loop between cardiopulmonary mesoderm and the foregut endoderm for endodermal pulmonary specification and, subsequently, atrial septation. We show that Tbx5 is required for pulmonary specification in mice and amphibians but not for swim bladder development in zebrafish. TBX5 is non-cell-autonomously required for pulmonary endoderm specification by directly driving Wnt2 and Wnt2b expression in cardiopulmonary mesoderm. TBX5 ChIPsequencing identified cis-regulatory elements at Wnt2 sufficient for endogenous Wnt2 expression domains in vivo and required for Wnt2 expression in precardiac mesoderm in vitro. Tbx5 cooperated with Shh signaling to drive Wnt2b expression for lung morphogenesis. Tbx5 haploinsufficiency in mice, a model of Holt-Oram syndrome, caused a quantitative decrement of mesodermal-to-endodermal Wnt signaling and subsequent endodermal-to-mesodermal Shh signaling required for cardiac morphogenesis. Thus, Tbx5 initiates a mesodermendoderm-mesoderm signaling loop in lunged vertebrates that provides a molecular basis for the coevolution of pulmonary and cardiac structures required for terrestrial life. lung development | heart development | TBX5 | Wnt signaling | Hedgehog signaling

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Various diseases severely affect Brassica crops, leading to significant global yield losses and a reduction in crop quality. In this study, we used the complete protein sequences of 49 cloned resistance genes (R genes) that confer resistance to fungal and bacterial diseases known to impact species in the Brassicaceae family. Homology searches were carried out across Brassica napus, B. rapa, B. oleracea, B. nigra, B. juncea, B. carinata and Arabidopsis thaliana genomes. In total, 660 cloned disease R gene homologs (CDRHs) were identified across the seven species, including 431 resistance gene analogs (RGAs) (248 nucleotide binding site-leucine rich repeats (NLRs), 150 receptor-like protein kinases (RLKs) and 33 receptor-like proteins (RLPs)) and 229 non-RGAs. Based on the position and distribution of specific homologs in each of the species, we observed a total of 87 CDRH clusters composed of 36 NLR, 16 RLK and 3 RLP homogeneous clusters and 32 heterogeneous clusters. The CDRHs detected consistently across the seven species are candidates that can be investigated for broad-spectrum resistance, potentially providing resistance to multiple pathogens. The R genes identified in this study provide a novel resource for the future functional analysis and gene cloning of Brassicaceae R genes towards crop improvement.

An understanding of genetic diversity and the population genetic processes that impact future population viability is vital for the management and recovery of declining populations of threatened species. Styphelia longissima (Ericaceae) is a critically endangered shrub, restricted to a single fragmented population near Eneabba, 250 km north of Perth, Western Australia. For this population, we sought to characterize population genetic variation and its spatial structure, and aspects of the mating portfolio, from which strategies that optimize the conservation of this diversity are identified. A comprehensive survey was carried out and 220 adults, and 106 seedlings from 14 maternal plants, were genotyped using 13 microsatellite markers. Levels of genetic variation and its spatial structure were assessed, and mating system parameters were estimated. Paternity was assigned to the offspring of a subsection of plants, which allowed for the calculation of realized pollen dispersal. Allelic richness and levels of expected heterozygosity were higher than predicted for a small isolated population. Spatial autocorrelation analysis identified fine-scale genetic structure at a scale of 20 m, but no genetic structure was found at larger scales. Mean outcrossing rate (tm = 0.66) reflects self-compatibility and a mixed-mating system. Multiple paternity was low, where 61 % of maternal siblings shared the same sire. Realized pollen dispersal was highly restricted, with 95 % of outcrossing events occurring at 7 m or less, and a mean pollen dispersal distance of 3.8 m. Nearest-neighbour matings were common (55 % of all outcross events), and 97 % of mating events were between the three nearest-neighbours. This study has provided critical baseline data on genetic diversity, mating system and pollen dispersal for future monitoring of S. longissima. Broadly applicable conservation strategies such as implementing a genetic monitoring plan, diluting spatial genetic structure in the natural population, genetically optimizing ex situ collections and incorporating genetic knowledge into translocations will help to manage the future erosion of the high genetic variation detected.

The Brassica genus contains abundant economically important vegetable and oilseed crops, which are under threat of diseases caused by fungal, bacterial and viral pathogens. Resistance gene analogues (RGAs) are associated with quantitative and qualitative disease resistance and the identification of candidate RGAs associated with disease resistance is crucial for understanding the mechanism and management of diseases through breeding. The availability of Brassica genome assemblies has greatly facilitated reference-based quantitative trait loci (QTL) mapping for disease resistance. In addition, pangenomes, which characterise both core and variable genes, have been constructed for B. rapa, B. oleracea and B. napus. Genome-wide characterisation of RGAs using conserved domains and motifs in reference genomes and pangenomes reveals their clustered arrangements and presence of structural variations. Here, we comprehensively review RGA identification in important Brassica genome and pangenome assemblies. Comparison of the RGAs in QTL between resistant and susceptible individuals allows for efficient identification of candidate disease resistance genes. However, the reference-based QTL mapping and RGA candidate identification approach is restricted by the under-represented RGA diversity characterised in the limited number of Brassica assemblies. The species-wide repertoire of RGAs make up the pan-resistance gene analogue genome (pan-RGAome). Building a pan-RGAome, through either whole genome resequencing or resistance gene enrichment sequencing, would effectively capture RGA diversity, greatly expanding breeding resources that can be utilised for crop improvement.