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Salinity and waterlogging interact to reduce growth for most crop and pasture species. The combination of these stresses often cause a large increase in the rate of Na+ and Cl− transport to shoots; however, the mechanisms responsible for this are largely unknown. To identify mechanisms contributing to the adverse interaction between salinity and waterlogging, we compared two Lotus species with contrasting tolerances when grown under saline (200 m M NaCl) and O2-deficient (stagnant) treatments. Measurements of radial O2 loss (ROL) under stagnant conditions indicated that more O2 reaches root tips of Lotus tenuis, compared with Lotus corniculatus. Better internal aeration would contribute to maintaining Na+ and Cl− transport processes in roots of L. tenuis exposed to stagnant-plus-NaCl treatments. L. tenuis root Na+ concentrations after stagnant-plus-NaCl treatment (200 m M) were 17% higher than L. corniculatus, with 55% of the total plant Na+ being accumulated in roots, compared with only 39% for L. corniculatus. L. tenuis accumulated more Na+ in roots, presumably in vacuoles, thereby reducing transport to the shoot (25% lower than L. corniculatus). A candidate gene for vacuole Na+ accumulation, an NHX1-like gene, was cloned from L. tenuis and identity established via sequencing and yeast complementation. Transcript levels of NHX1 in L. tenuis roots under stagnant-plus-NaCl treatment were the same as for aerated NaCl, whereas L. corniculatus roots had reduced transcript levels. Enhanced O2 transport to roots enables regulation of Na+ transport processes in L. tenuis roots, contributing to tolerance to combined salinity and waterlogging stresses. [ABSTRACT FROM AUTHOR]

A total of 103 root nodule isolates were used to estimate the diversity of bacteria nodulating Lotus tenuis in typical soils of the Salado River Basin. A high level of genetic diversity was revealed by repetitive extragenic palindromic PCR, and 77 isolates with unique genomic fingerprints were further differentiated into two clusters, clusters A and B, after 16S rRNA restriction fragment length polymorphism analysis. Cluster A strains appeared to be related to the genus Mesorhizobium, whereas cluster B was related to the genus Rhizobium. 16S rRNA sequence and phylogenetic analysis further supported the distribution of most of the symbiotic isolates in either Rhizobium or Mesorhizobium: the only exception was isolate BA135, whose 16S rRNA gene was closely related to the 16S rRNA gene of the genus Aminobacter. Most Mesorhizobium-like isolates were closely related to Mesorhizobium amorphae, Mesorhizobium mediterraneum, Mesorhizobium tianshanense, or the broad-host-range strain NZP2037, but surprisingly few isolates grouped with Mesorhizobium loti type strain NZP2213. Rhizobium-like strains were related to Rhizobium gallicum, Rhizobium etli,or Rhizobium tropici, for which Phaseolus vulgaris is a common host. However, no nodC or nifH genes could be amplified from the L. tenuis isolates, suggesting that they have rather divergent symbiosis genes. In contrast, nodC genes from the Mesorhizobium and Aminobacter strains were closely related to nodC genes from narrow-host-range M. loti strains. Likewise, nifH gene sequences were very highly conserved among the Argentinian isolates and reference Lotus rhizobia. The high levels of conservation of the nodC and nifH genes suggest that there was a common origin of the symbiosis genes in narrow-host-range Lotus symbionts, supporting the hypothesis that both intrageneric horizontal gene transfer and intergeneric horizontal gene transfer are important mechanisms for the spread of symbiotic capacity in the Salado River Basin. [ABSTRACT FROM AUTHOR]

Development of the unisexual maize inflorescences requires the abortion of pistillate primordia in the florets of the developing tassel and the arrest of staminate primordia in the florets of the developing ears. Mutations of many genes that lie within this sexual differentiation pathway, such as tasselseed1 ( ts1), or that influence this pathway, such as mediator of paramutation 1 ( mop1), result in feminization of the normally male tassel. Here, we show the loss of mop1 or ts1 function results in increased mRNA levels for several members of the SBP-box gene family. Our analyses of this family expand the number of maize SBP-box genes from 9 to 31 members. Intron–exon structures as well as phylogenetic data support the division of these family members into six groups. The SBP-box genes upregulated in feminized tassels fall into two groups, share common structural motifs and include the presence of a target site for miR156. Small RNA blots show miR156 levels are decreased in both mop1 and ts1 mutants. While there is a correlation between miR156 levels and SBP-box gene transcript levels, this correlation is not absolute, and thus we hypothesize that decreased levels of miR156 may provide competency for SBP-box gene upregulation by other common factors yet to be identified. We present a model that provides a putative link between ts1, ts2, ts4, Ts6, and mop1 in the sex-determination pathway. [ABSTRACT FROM AUTHOR]

Two meiotic mutants of L. tenuis (2n = 2x = 12) producing unreduced pollen are described When crossed to male sterile L eornlculatu3 (2n = 4x = 24) plants, all progeny plants were morphologically similar to L. corniculatus had 2n = 24 chromosomes, and in the cross, were fully compatible with L. corniculatus, indicating that the male parent plants were 2n-pollen producers. One of them also had 'giant' pollen grains In metaphase 11 of both genotypes. there were parallel and tripolar spindles leading to dyad and triad formation, the latter being found most frequently. Since both the above-mentioned mechanisms result in first-division restitution-type microspores. the genotypes examined could be useful in breeding Lotus. [ABSTRACT FROM AUTHOR]

The narrow-leaf trefoil is a widely used forage plant in temperate and subtemperate areas. It is the object of extensive improvement programs and research, which has generated a large body of literature. A few decades ago it was discovered that its traditional scientific name, Lotus tenuis Waldst. & Kit. ex Willd., had to be superseded by an older name, L. glaber Mill. It was then proposed to permanently reject the name L. glaber, thus allowing L. tenuis to continue in use for the narrow-leaf trefoil. The rejection proposal for the name L. glaber was finally accepted by the 17th International Botanical Congress (IBC) in July 2005, so L. tenuis is now the scientific name for the narrow-leaf trefoil. [ABSTRACT FROM AUTHOR]