Late Campanian fossil of a legume fruit supports Mexico as a center of Fabaceae radiation

An mTRAN-mRNA interaction mediates mitochondrial translation initiation in plants

Plant mitochondria represent the largest group of respiring organelles on the planet. Plant mitochondrial messenger RNAs (mRNAs) lack Shine-Dalgarno-like ribosome-binding sites, so it is unknown how plant mitoribosomes recognize mRNA. We show that "mitochondrial translation factors" mTRAN1 and mTRAN2 are land plant-specific proteins, required for normal mitochondrial respiration chain biogenesis. Our studies suggest that mTRANs are noncanonical pentatricopeptide repeat (PPR)-like RNA binding proteins of the mitoribosomal "small" subunit. We identified conserved Adenosine (A)/Uridine (U)-rich motifs in the 5' regions of plant mitochondrial mRNAs. mTRAN1 binds this motif, suggesting that it is a mitoribosome homing factor to identify mRNAs. We demonstrate that mTRANs are likely required for translation of all plant mitochondrial mRNAs. Plant mitochondrial translation initiation thus appears to use a protein-mRNA interaction that is divergent from bacteria or mammalian mitochondria.

Legumes from the Paleocene sediments of India and their ecological significance

During the early Paleogene, greenhouse gases created warm global climates. These warm climates redistributed the habitat of marine and terrestrial biota globally. Understanding the ecology of biotas under extremely warm climates is important to decipher their behavior in future climate warming. Here we report two new legume fossils (Leguminocarpum meghalayensis Bhatia, Srivastava et Mehrotra sp. nov., and Parvileguminophyllum damalgiriensis Bhatia, Srivastava et Mehrotra sp. nov.) from the late Paleocene sediments of Tura Formation of Meghalaya, northeast India. Globally, the Paleocene legume fossil records indicate that legumes most likely immigrated to India from Africa via the Ladakh-Kohistan Arc during the early Paleogene. Moreover, previously reconstructed climate data from the Tura Formation indicate that legumes were well adapted to a warm seasonal climate with monsoon rains.

Nodules of wild legumes as unique natural hotspots of antibiotic resistance genes

Root nodules (RN) of legumes have distinct microenvironment from their symbiotic roots and surrounding soils. The rhizobia can withstand the host-produced phytoalexins and antimicrobial compounds. We thus hypothesize that the wild legume RN may develop unique natural resistome and be antibiotic resistance gene (ARG) hotspots. In this study, in comparison with rhizosphere soil (RS) and bulk soil (BS), we characterized the feature of antibiotic resistance in the RN of two wild legumes, Medicago polymorpha and Astragalus sinicus, by metagenomics. It was shown that the total relative abundance of ARGs followed the order of RN > RS > BS for both legumes. ARGs encoding antibiotic efflux pump predominated in all samples with increased proportion from BS to RN samples for both legumes. Totally 275 ARG subtypes were detected, and diversity of ARGs in RN was significantly lower than in BS samples for both legumes. 32 and 25 unique ARGs subtypes were detected in RN of both legumes. Bacterial community played a key role in shaping nodule-associated resistome because both ARG profiles and bacterial community differed greatly among BS, RS and RN. Rhizobia potentially hosted 10 and 15 ARGs subtypes for both legumes. The number and proportion of plasmid- and ARG-carrying contigs (ACCs) were higher in RN than in BS. Host tracking analysis of plasmid-ACCs suggests that proportion of rhizobial bacteria identified as their hosts decreased from BS to RN samples. No plasmid-ACCs with multiple ARGs were observed in BS samples, whereas they were detected in RN samples of both legumes. Our study showed that even wild legume nodules are unique natural ARG hotspots and enough attention should be paid to the dissemination risk of ARGs posed by globally produced legume crops.

Mezcala - a new segregate genus of mimosoid legume (Leguminosae, Caesalpinioideae, mimosoid clade) narrowly endemic to the Balsas Depression in Mexico

Recent results have demonstrated that the genus Desmanthus is non-monophyletic because the genus Kanaloa is nested within it, with a single species, Desmanthusbalsensis placed as sister to the clade comprising Kanaloa plus the remaining species of Desmanthus. Here we transfer D.balsensis to a new segregate genus Mezcala, discuss the morphological features supporting this new genus, present a key to distinguish Mezcala from closely related genera in the Leucaena subclade, and provide a distribution map of M.balsensis.

Fossil papilionoids of the Bowdichia clade (Leguminosae) from the Paleogene of North America

PREMISE

Understanding the evolutionary history of flowering plants has been enriched by the integration of molecular phylogenies and evidence from the fossil record. Fossil fruits and leaves from the late Paleocene and Eocene of Wyoming and Eocene of Kentucky and Tennessee are described as extinct genera in the tropical American Bowdichia clade of the legume subfamily Papilionoideae. Recent phylogenetic study and taxonomic revision of the Bowdichia clade have facilitated understanding of relationships of the fossil taxa and their evolutionary implications and paleoenvironmental significance.

METHODS

The fossils were studied using standard methods of specimen preparation and light microscopy and compared to fruits and leaves from extant legume taxa using herbarium collections. Phylogenetic relationships of the fossil taxa were assessed using morphology and DNA sequence data.

RESULTS

Two new fossil genera are described and their phylogenetic relationships are established. Paleobowdichia lamarensis is placed as sister to the extant genus Bowdichia and Tobya claibornensis is placed with the extant genera Guianodendron and Staminodianthus.

CONCLUSIONS

These fossils demonstrate that the tropical American Bowdichia clade was present in North America during a period when tropical or subtropical conditions prevailed in the northern Rocky Mountains during the late Paleocene and the Mississippi Embayment during the middle Eocene. These fossils also document that the Bowdichia clade had diversified by the late Paleocene when the fossil record of the family is relatively sparse. This result suggests that future work on early fossil legumes should focus on tropical and subtropical climatic zones, wherever they may occur latitudinally.

New Skull Material of Taeniolabis taoensis (Multituberculata, Taeniolabididae) from the Early Paleocene (Danian) of the Denver Basin, Colorado

Taeniolabis taoensis is an iconic multituberculate mammal of early Paleocene (Puercan 3) age from the Western Interior of North America. Here we report the discovery of significant new skull material (one nearly complete cranium, two partial crania, one nearly complete dentary) of T. taoensis in phosphatic concretions from the Corral Bluffs study area, Denver Formation (Danian portion), Denver Basin, Colorado. The new skull material provides the first record of the species from the Denver Basin, where the lowest in situ specimen occurs in river channel deposits ~730,000 years after the Cretaceous-Paleogene boundary, roughly coincident with the first appearance of legumes in the basin. The new material, in combination with several previously described and undescribed specimens from the Nacimiento Formation of the San Juan Basin, New Mexico, is the subject of detailed anatomical study, aided by micro-computed tomography. Our analyses reveal many previously unknown aspects of skull anatomy. Several regions (e.g., anterior portions of premaxilla, orbit, cranial roof, occiput) preserved in the Corral Bluffs specimens allow considerable revision of previous reconstructions of the external cranial morphology of T. taoensis. Similarly, anatomical details of the ascending process of the dentary are altered in light of the new material. Although details of internal cranial anatomy (e.g., nasal and endocranial cavities) are difficult to discern in the available specimens, we provide, based on UCMP 98083 and DMNH.EPV 95284, the best evidence to date for inner ear structure in a taeniolabidoid multituberculate. The cochlear canal of T. taoensis is elongate and gently curved and the vestibule is enlarged, although to a lesser degree than in Lambdopsalis.