Ann M. Hirsch

University of California, Los Angeles

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Michelle R. Lum

Loyola Marymount University

Nancy A. Fujishige

Loyola Marymount University

Maskit Maymon

University of California, Los Angeles

Ethan Humm

University of California, Los Angeles

Paulina Estrada‐de los Santos

Instituto Politécnico Nacional

Noor Khan

University of California, Los Angeles

Pilar Martínez‐Hidalgo

Universidad de Salamanca

Akihiro Suzuki

Saitama Prefectural Education Center

Laurence M. Brill

Sanford Burnham Prebys Medical Discovery Institute

Heather I. McKhann

Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement

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University of California, Los Angeles

124

Lawrence Berkeley National Laboratory

Joint Genome Institute

University of California, Berkeley

University of California, Davis

United States Department of Energy

Michigan State University

Oak Ridge National Laboratory

University of Wisconsin–Madison

Saga University

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Nodule Development in Legumes—The Early Stages: Involvement of Early Nodulins, Lectins, and Other Proteins

Current plant science and biotechnology in agriculture (1995)

Ann M. Hirsch Yiwen Fang Laurence M. Brill Keith L. Wycoff Bettina M. Niner

Nodule (geology)

Primordium

Nod factor

10.1007/978-94-011-0379-4_37

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Citations (2)

Symbiotic mutants of rhizobium meliloti that uncouple plant from bacterial differentiation

Cell (1985)

Turlough M. Finan Ann M. Hirsch John A. Leigh Eric Johansen Gretchen A. Kuldau

Root hair

Nodule (geology)

10.1016/0092-8674(85)90346-0

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Citations (337)

Soil microbiomes from the Groundnut basin of Senegal contain plant growth-promoting bacteria with potential for crop improvement in arid soils

Canadian Journal of Microbiology (2024)

Niokhor Bakhoum Ethan Humm Noor Khan Ann M. Hirsch

The principal methods to maintain soil fertility in Sahel soils are largely allowing fields to go fallow and manure addition. These methods are not currently sufficient to improve soil fertility. To promote biological amendments, we aimed to understand the plant-growth promoting traits of various soil microbial isolates. The soils collected in different areas in Senegal exhibited a similar eDNA profile of bacteria; the dominant microbes were Firmicutes, followed by Proteobacteria and Actinobacteria. Of 17 isolates identified and tested, the vast majority solubilized rock phosphate and a large number grew on culture medium containing 6% salt, but very few degraded starches or hydrolysed carboxymethyl cellulose or produced siderophores. Upon single inoculation, Peribacillus asahii RC16 and Dietzia cinnamea 55 significantly increased pearl millet growth and yield parameters. For cowpea, plant shoot length was significantly increased by Pseudarthrobacter phenanthrenivorans MKAG7 co-inoculated with Bradyrhizobium elkanii 20TpCR5, and nearly all rhizobacteria tested significantly improved cowpea dry weight and pod weight. Additionally, the double inoculation of Dietzia cinnamea 55 and MKAG7 significantly increased shoot length, dry weight, and seed head weight of pearl millet. These isolates are promising inoculants because they are ecologically-friendly, cost-effective, sustainable, and have fewer negative effects on the soil and its inhabitants.

Bradyrhizobium

10.1139/cjm-2024-0031

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A feeling for the micro-organism: structure on a small scale. Biofilms on plant roots - eScholarship

Nancy A. Fujishige Neel N. Kapadia Ann M. Hirsch

Biofilms are structured communities of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface; they have clinical, industrial and environmental impacts. Biofilms that are established by bacteria on plants are found on the surfaces of roots, leaves, seeds and internal vascular tissues where the microbes live in commensal, mutualistic or parasitic/pathogenic associations with their host. The study of the structure of plant-associated biofilms has been considerably helped by the development of techniques using fluorescent markers coupled with confocal scanning laser microscopy as well as scanning electron microscopy. We review several of these techniques as well as some of the research that has dealt with plant-associated biofilms. Our investigations focus on biofilm formation in the early stages of the Rhizobium-legume symbiosis, in which Gram-negative rhizobia provide fixed nitrogen to a host legume, and in return, the legume provides carbon-containing molecules. Because root colonization is an important early step in the establishment of the nitrogen-fixing symbiosis, we looked at Sinorhizobium meliloti attachment and biofilm establishment on the roots of its legume hosts, Medicago sativa L. and Melilotus alba Desr. We also examined biofilm formation by Rhizobium leguminosarum bv. viciae on the roots of Arabidopsis thaliana ( L.) Heynh., a non-legume and non-host. Our ultimate goal is to characterize the rhizobial genes involved in aggregation and attachment to roots because several of these appear to be shared in biofilm formation and rhizobial entry of legume root cells. (c) 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 79-88.

Sinorhizobium meliloti

Medicago truncatula

Rhizobium leguminosarum

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Structural Investigations of Asexual Reproduction in Nephrolepis exaltata and Platycerium bifurcatum

American Journal of Botany (1983)

Jennifer H. Richards Judith Zenk Beck Ann M. Hirsch

Stolon

Primordium

Asexual reproduction

Leafy

Apex (geometry)

Budding

10.2307/2442807

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Citations (7)

Choreographing the Complex Interaction between Legumes and α- and β-Rhizobia

Angie Lee Ann M. Hirsch

The nitrogen-fixing symbiosis between bacteria in the family Rhizobiaceae and members of the legume family (Fabaceae) has been well studied, particularly from the perspective of the early signaling and recognition events. Recent studies of non-nodulating legume mutants have resulted in the identification of a number of genes that are responsive to signal molecules from the bacteria. However, a second group of nodule-forming bacteria, completely unrelated to the Rhizobiaceae, which are α-Proteobacteria, has been discovered. These bacteria belong to the β-Proteobacteria and have been designated β-rhizobia to distinguish them from the better-known α-rhizobia. Here, we review what is known in this economically important symbiosis about the interaction between legumes and α-rhizobia, and we incorporate information, where known, about the β-rhizobia.

Nod factor

Sinorhizobium

Sinorhizobium meliloti

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Impact of Soil Salinity on the Cowpea Nodule-Microbiome and the Isolation of Halotolerant PGPR Strains to Promote Plant Growth under Salinity Stress

Phytobiomes Journal (2020)

Salma Mukhtar Ann M. Hirsch Noor Khan K. A. Malik Ethan Humm

Cowpea is one of the major legumes cultivated in arid and semiarid regions of the world. Four soil-microbial samples (SS-1 through SS-4) collected from semiarid soils in Punjab, Pakistan were planted with cowpea (Vigna unguiculata) crops, which were grown under salinity stress to analyze bacterial composition in the rhizosphere and within nodules using cultivation-dependent and -independent methods. Two varieties, 603 and the salt-tolerant CB 46, were each inoculated with or without the four different native soil samples or grown in medium either N-deficient (−N) or supplemented with N (+N). Plants inoculated with soil samples SS-2 and SS-4 grew better than plants inoculated with SS-1- and SS-3 and grew comparably with the +N controls. Environmental DNA (eDNA) was isolated from SS-1 and SS-4, and, by 16S ribosomal RNA sequencing, the soil microbiomes consisted mainly of Actinobacteria, Firmicutes, Proteobacteria, and other nonproteobacterial genera. However, analysis of eDNA isolated from cowpea nodules established by the trap plants showed that the nodule microbiome consisted almost exclusively of proteobacterial sequences, particularly species of Bradyrhizobium. Bacteria were isolated from both soils and nodules, and 34 of the 51 isolates tested positive for plant-growth-promoting rhizobacteria traits in plate assays. Many could serve as future inocula for crops in arid soils. The discrepancy between the types of bacteria isolated by culturing bacteria isolated from surface-sterilized cowpea nodules (proteobacteria and nonproteobacteria) versus those detected by sequencing DNA isolated from the nodules (proteobacteria) from cowpea nodules (proteobacteria and nonproteobacteria) versus those detected in the nodule microbiome (proteobacteria) needs further study.

Bradyrhizobium

Halotolerance

10.1094/pbiomes-09-19-0057-r

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Citations (17)

Chloroplasts in Living Cells and the String-of-Grana Concept of Chloroplast Structure Revisited

Photosynthesis Research (2004)

S. G. Wildman Ann M. Hirsch Stefan J. Kirchanski Donald Spencer

10.1023/b:pres.0000030423.84134.3c

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Citations (19)

Developmental biology of legume nodulation

New Phytologist (1992)

Ann M. Hirsch

SUMMARY Many legumes respond to Rhizobium inoculation by developing unique structures known as nodules on their roots. The development of a legume nodule in which rhizobia convert atmospheric N 2 into ammonia is a finely tuned process. Gene expression from both partners of the symbiosis must be temporally and spatially coordinated. Exactly how this coordination takes place is an area of intense study. Nodule morphogenesis appears to be elicited by at least two distinct signals: one from Rhizobium , a product of the nod genes (Nod factor), and a second signal, which is generated within plant tissues after treatment with Nod factor. The identity of the second signal is unknown but changes in the balance of endogenous plant hormones or the sensitivity of plant tissues to these hormones are likely to be involved. These hormonal changes may be triggered by endogenous flavonoids produced by the root in response to inoculation with Rhizobium. There is some controversy as to whether the legume nodule is an organ sui generis or a highly derived lateral root. A resolution of this question may become more critical as attempts to induce nodules on non‐legume hosts, such as rice or maize, increase in number and scope. CONTENTS Summary 211 I. Introduction 211 II. Nodule development 213 III. Nodule initiation 220 IV. The second signal for nodule morphogenesis: role for the plant hormones ? 225 V. Lateral root development 229 VI. Are nodules modified lateral roots ? 229 VII. Conclusions and future prospects 231 Acknowledgements and dedication 232 References 232

Nod factor

Nodule (geology)

Root hair

Lateral root

10.1111/j.1469-8137.1992.tb04227.x

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Citations (618)

In-situ hybridization of nodulin mRNAs in root nodules using non-radioactive probes

Plant Molecular Biology Reporter (1991)

Birgit Bochenek Ann M. Hirsch

10.1007/bf02672070

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Citations (2)