Ann M Hirsch | University of California, Los Angeles (original) (raw)

Papers by Ann M Hirsch

Metaverse creativity, Dec 1, 2013

Journal of Plant Research, Jan 19, 2008

John Wiley & Sons, Inc. eBooks, Jul 14, 2015

Physiologia Plantarum, Jun 1, 2007

Glycosyltransferases (GTs) play diverse roles in cellular metabolism by modifying the activities ... more Glycosyltransferases (GTs) play diverse roles in cellular metabolism by modifying the activities of structural and regulatory metabolites. Previous studies indicated that a Pisum sativum UDP-glycosyltransferase (PsUGT1) is essential for plant development, and suggested a role for this enzyme in the regulation of the cell division cycle. Here we report that recombinant PsUGT1 expressed in vitro exhibits activity on diverse flavonoids including kaempferol. In Arabidopsis expressing PsUGT1, gravity sensing is impaired, and this loss of function is corrected by exogenous addition of kaempferol. HPLC of tissue extracts of Arabidopsis expressing PsUGT1 revealed the accumulation of glycosides of kaempferol, but not of other related flavonoids. A search of the NCBI gene bank (http://www.ncbi.nlm.nih.gov/) using PsUGT1 revealed that six genes from the Arabidopsis AtUGT85A subfamily show similarities both in DNA and protein sequences (Woo et al. 2007). In the current study, we examined the hypothesis that one or more members of this family, like PsUGT1, is required for Arabidopsis development. Altered expression of AtUGT85A7, but not other AtUGT85A subfamily members, resulted in changes in life cycle, leaf morphology, auxin response, and root development, including loss of gravity sensing. The phenotypes of plants where AtUGT85A7 gene expression was suppressed, by RNAi mutagenesis, were very similar to those occurring in plants with altered expression of PsUGT1.

Journal of Bacteriology, Mar 1, 1987

Current plant science and biotechnology in agriculture, 1987

The ability of critical symbiotic functions to be provided to one bacterium by another (i.e., in ... more The ability of critical symbiotic functions to be provided to one bacterium by another (i.e., in trans) during the course of nodule development has been examined with derivatives of the alfalfa symbiont R. meliloti SU47.

Revista latinoamericana de microbiología, 1993

The involvement of root hairs in the establishment of the Rhizobium-legume symbiosis is well know... more The involvement of root hairs in the establishment of the Rhizobium-legume symbiosis is well known although the root hair is by no means the only point of entry of the bacteria into the plant root. A number of legumes are invaded by the so-called “crack entry” mode of penetration (Sprent 1989) whereby rhizobia enter the root either between epidermal cells or through breaks made through the root cortex by elongating lateral roots. In root hair entry, rhizobia dock on the root hairs, which deform in response to secreted Nod factors, and then the rhizobia enter the curled root hair by means of an infection thread (see Chapter 15 this volume).

Advances in Experimental Medicine and Biology, 2002

1. BACKGROUND More than 4,000 different flavonoids, which are widely distributed in higher plants... more 1. BACKGROUND More than 4,000 different flavonoids, which are widely distributed in higher plants, have been identified (Harbome, 1988; Koes et al. 1994). Flavonoids are involved in numerous functions in vascular plants. One obvious function is as a filter for ...

Current Opinion in Plant Biology, Aug 1, 1999

Proceedings of the National Academy of Sciences of the United States of America, Feb 1, 1989

Rhizobium nod genes are essential for root hair deformation and cortical cell division, early sta... more Rhizobium nod genes are essential for root hair deformation and cortical cell division, early stages in the development ofnitrogen-fixing root nodules. Nod-mutants are unable to initiate nodules on legume roots. We observed that N-(1-naphthyl)phthalamic acid and 2,3,5-triiodobenzoic acid, compounds known to function as auxin transport inhibitors, induced nodule-like structures on alfalfa roots. The nodule-like structures (pseudonodules) were white, devoid of bacteria, and resembled nodules elicited by Rhizobium meliloti exopolysaccharide (exo) mutants at both the histological and molecular level. Two nodulin genes, ENOD2 and Nms-30, were expressed. RNA isolated from the nodule-like structures hybridized to pGmENOD2, a soybean early nodulin cDNA clone. RNA isolated from roots did not hybridize. We determined by in vitro translations of total RNA that the alfalfa nodulin transcript Nms-30 was also expressed in the nodule-like structures. The late expressed nodulin genes, such as the leghemoglobin genes, were not transcribed. Because N-(1-naphthyl)phthalamic acid and 2,3,5-triiodobenzoic acid induce the development of nodules on alfalfa roots, we suggest that the auxin transport inhibitors nmimic the activity of compound(s) made upon the induction of the Rhizobium nod genes. The nodulation (nod) genes of Rhizobium play an essential role in the induction of nodules on the roots of leguminous plants. The importance of the nod genes has been demonstrated in at least two ways. First, it has been shown that Rhizobium that have mutated common nod genes, nodABC, lose the ability to curl root hairs (1) as well as to initiate cellular divisions within the root cortex. Cortical cell divisions mark the beginning of root nodule formation (2). Second, by transferring the nod region of Rhizobium meliloti or Rhizobium leguminosarum to Agrobacterium tumefaciens, Agrobacterium transconjugants acquire the ability to form nodules on alfalfa and Vicia, respectively (3, 4). Although the nod genes are required for the earliest stages

HAL (Le Centre pour la Communication Scientifique Directe), 2008

John Wiley & Sons, Inc. eBooks, Mar 18, 2013

Summary of known bioﬁlm-forming rhizosphere bacteria Organism Phenotype Relevant Characteristics ... more Summary of known bioﬁlm-forming rhizosphere bacteria Organism Phenotype Relevant Characteristics Reference Acinetobacter calcoaceticus P23 Root colonization of duckweed PGPB, bioremediation Yamaga et al. (2010) Agrobacterium tumefaciens Disease of pea Pathogenesis Hawes and Smith (1989) Azorhizobium brasilense Root colonization of wheat PGPR Kim et al. (2005) Azorhizobium caulinodans Root colonization of rice PGPR Van Nieuwenhove et al. (2000) Bacillus amyloliquefaciens S499Root colonization of tomato,maize, and Arabidopsisthaliana PGPB, biocontrol Nihorimbere et al. (2012);Fan et al. (2011) Bacillus cereus and Bacilluspumilus Root colonization of wildbarley found in theEvolution Canyon, IsraelSalt, heat, and desiccationtoleranceTimmusk et al. (2011) Bacillus polymyxa Root colonization of cucumber PGPB Yang et al. (2004) Bacillus subtilis Root colonization of Arabidopsis thaliana Biocontrol Rudrappa and Bais (2007) Burkholderia cepacia and Burkholderia cenocepacia Diseases of onion and wheat Pathogenesis Ellis and Cooper (2010);Jacobs et al. (2008);Balandreau et al. (2001)