Kazumi Hattori

Bio: Kazumi Hattori is an academic researcher from Nagoya University. The author has contributed to research in topics: Shoot & Callus. The author has an hindex of 18, co-authored 56 publications receiving 1387 citations.

Enhanced salt tolerance mediated by AtHKT1 transporter-induced Na unloading from xylem vessels to xylem parenchyma cells.

Abstract: Summary AtHKT1 is a sodium (Na+) transporter that functions in mediating tolerance to salt stress. To investigate the membrane targeting of AtHKT1 and its expression at the translational level, antibodies were generated against peptides corresponding to the first pore of AtHKT1. Immunoelectron microscopy studies using anti-AtHKT1 antibodies demonstrate that AtHKT1 is targeted to the plasma membrane in xylem parenchyma cells in leaves. AtHKT1 expression in xylem parenchyma cells was also confirmed by AtHKT1 promoter–GUS reporter gene analyses. Interestingly, AtHKT1 disruption alleles caused large increases in the Na+ content of the xylem sap and conversely reduced the Na+ content of the phloem sap. The athkt1 mutant alleles had a smaller and inverse influence on the potassium (K+) content compared with the Na+ content of the xylem, suggesting that K+ transport may be indirectly affected. The expression of AtHKT1 was modulated not only by the concentrations of Na+ and K+ but also by the osmolality of non-ionic compounds. These findings show that AtHKT1 selectively unloads sodium directly from xylem vessels to xylem parenchyma cells. AtHKT1 mediates osmolality balance between xylem vessels and xylem parenchyma cells under saline conditions. Thus AtHKT1 reduces the sodium content in xylem vessels and leaves, thereby playing a central role in protecting plant leaves from salinity stress.

Characterization of XET-Related Genes of Rice

Abstract: To elucidate the mechanism of internodal elongation in rice (Oryza sativa L), we analyzed genes encoding xyloglucan endotransglycosylase (XET), a cell wall-loosening enzyme essential for cell elongation Four rice XET-related (XTR) genes, OsXTR1, OsXTR2, OsXTR3, and OsXTR4, were isolated and their expression patterns in rice plants determined The expression of the four XTR genes showed different patterns of organ specificity and responses to several plant hormones OsXTR1 and OsXTR3 were up-regulated by gibberellin and brassinosteroids, whereas OsXTR2 and OsXTR4 showed no clear response to these hormones Expression of the four XTR genes was also investigated in elongating internodes at different developmental stages OsXTR1 and OsXTR3 were preferentially expressed in the elongating zone of internodes, while OsXTR2 and OsXTR4 were expressed in nodes and in the divisional and elongating zones of internodes In three genetic mutants with abnormal heights, the expression of OsXTR1 and OsXTR3 correlated with the height of the mutants, whereas no such correlation was observed for OsXTR2 and OsXTR4 Based on these observations, we discuss the roles that OsXTR1 and OsXTR3 may play in internodal elongation in rice

A combination of thidiazuron and benzyladenine promotes multiple shoot production from cotyledonary node explants of faba bean (Vicia faba L.)

Abstract: A procedure for multiple shoot formation from cotyledonary node explants of faba bean (Vicia faba LcvSGhdar) cultured on MS medium containing benzyladenine (BA) and thidiazuron (TDZ) was developed Explants on medium with TDZ in combination with BA produced a higher number of shoots than with either cytokinin alone The highest number of shoots was obtained when explants from 7-day-old seedlings were cultured on MS medium supplemented with TDZ and BA (2 mgl−1 each) for 31 days before transfer to hormone-free MS medium for elongation Shoots produced in vitro were rooted on half-strength agar-solidified MS basal medium or with 025 or 05 mgl−1 naphthalenacetic acid (NAA) prior to transfer to green house conditions This procedure was found to be applicable to seven other cultivars of faba bean from widely diverse provenances Thus, it can be advantageously applied to the production of transgenic faba bean plants

Ethylene inhibitors enhance in vitro root formation on faba bean shoots regenerated on medium containing thidiazuron

Abstract: The possible involvement of ethylene in in vitrorooting of faba bean (Vicia faba L.) shootsregenerated on medium containing thidiazuron wasinvestigated. The effects of the ethylene precursor1-aminocyclopropane-1-carboxylic acid (ACC) and threeethylene inhibitors, silver nitrate (AgNO3),acetyl salicylic acid (ASA) and cobalt chloride(CoCl2) on root formation were tested in vitrousing TDZ-induced shoots of faba bean accession 760.ACC inhibited root formation. In contrast, ethyleneinhibitors promoted root formation, AgNO3 at theappropriate concentrations enhanced root emergence andincreased root number per shoot, root growth rate, androot length. Both CoCl2 and ASA at theappropriate concentrations increased rootingefficiency. These promotive effects may result from areduction in ethylene concentration or inhibition ofethylene action. The results offer a new approach toimprove the rooting efficiency of TDZ-induced shootsof faba bean and possibly of other plant species.

High frequency shoot regeneration and plantlet formation from root tip of garlic

Abstract: An efficient and novel method of direct shoot regeneration from root tips in garlic was developed. The influence of growth regulators, basal media and age of root explant on shoot initiation and proliferation was examined. The best growth regulator combination was 1-naphthaleneacetic acid and 6-benzyladenine at 1 and 10 µM, respectively, inducing shoot initiation from 75% of the explants. The frequency of shoot initiation on different basal media was similar. Explant root tips from plantlets taken 15 to 18 days after sprouting showed the highest shoot initiation (95%). In contrast to Murashige and Skoog medium, which produced more than 10 shoots per explant, B5 medium produced smaller shoots, although the number was higher. Rooting of individual shoots was induced after transfer to medium without growth regulators. Plantlets, after acclimatization in a growth cabinet, were successfully transplanted to the field, and no phenotypic variation was observed among them. The technique has potential applicability for rapid propagation of garlic.

Mechanisms of salinity tolerance

Abstract: The physiological and molecular mechanisms of tolerance to osmotic and ionic components of salinity stress are reviewed at the cellular, organ, and whole-plant level. Plant growth responds to salinity in two phases: a rapid, osmotic phase that inhibits growth of young leaves, and a slower, ionic phase that accelerates senescence of mature leaves. Plant adaptations to salinity are of three distinct types: osmotic stress tolerance, Na + or Cl − exclusion, and the tolerance of tissue to accumulated Na + or Cl − . Our understanding of the role of the HKT gene family in Na + exclusion from leaves is increasing, as is the understanding of the molecular bases for many other transport processes at the cellular level. However, we have a limited molecular understanding of the overall control of Na + accumulation and of osmotic stress tolerance at the whole-plant level. Molecular genetics and functional genomics provide a new opportunity to synthesize molecular and physiological knowledge to improve the salinity tolerance of plants relevant to food production and environmental sustainability.

Potassium transport and plant salt tolerance.

Abstract: Salinity is a major abiotic stress affecting approximately 7% of the world's total land area resulting in billion dollar losses in crop production around the globe. Recent progress in molecular genetics and plant electrophysiology suggests that the ability of a plant to maintain a high cytosolic K+/Na+ ratio appears to be critical to plant salt tolerance. So far, the major efforts of plant breeders have been aimed at improving this ratio by minimizing Na+ uptake and transport to shoot. In this paper, we discuss an alternative approach, reviewing the molecular and ionic mechanisms contributing to potassium homeostasis in salinized plant tissues and discussing prospects for breeding for salt tolerance by targeting this trait. Major K+ transporters and their functional expression under saline conditions are reviewed and the multiple modes of their control are evaluated, including ameliorative effects of compatible solutes, polyamines and supplemental calcium. Subsequently, the genetic aspects of inheritance of K+ transport 'markers' are discussed in the general context of salt tolerance as a polygenic trait. The molecular identity of 'salt tolerance' genes is analysed, and prospects for future research and breeding are examined.

The XTH Family of Enzymes Involved in Xyloglucan Endotransglucosylation and Endohydrolysis: Current Perspectives and a New Unifying Nomenclature

Abstract: The polysaccharide xyloglucan is thought to play an important structural role in the primary cell wall of dicotyledons. Accordingly, there is considerable interest in understanding the biochemical basis and regulation of xyloglucan metabolism, and research over the last 16 years has identified a large family of cell wall proteins that specifically catalyze xyloglucan endohydrolysis and/or endotransglucosylation. However, a confusing and contradictory series of nomenclatures has emerged in the literature, of which xyloglucan endotransglycosylases (XETs) and endoxyloglucan transferases (EXGTs) are just two examples, to describe members of essentially the same class of genes/proteins. The completion of the first plant genome sequencing projects has revealed the full extent of this gene family and so this is an opportune time to resolve the many discrepancies in the database that include different names being assigned to the same gene. Following consultation with members of the scientific community involved in plant cell wall research, we propose a new unifying nomenclature that conveys an accurate description of the spectrum of biochemical activities that cumulative research has shown are catalyzed by these enzymes. Thus, a member of this class of genes/proteins will be referred to as a xyloglucan endotransglucosylase/hydrolase (XTH). The two known activities of XTH proteins are referred to enzymologically as xyloglucan endotransglucosylase (XET, which is hereby re-defined) activity and xyloglucan endohydrolase (XEH) activity. This review provides a summary of the biochemical and functional diversity of XTHs, including an overview of the structure and organization of the Arabidopsis XTH gene family, and highlights the potentially important roles that XTHs appear to play in numerous examples of plant growth and development.

Elucidating the molecular mechanisms mediating plant salt-stress responses

Abstract: Contents Summary 523 I. Introduction 523 II. Sensing salt stress 524 III. Ion homeostasis regulation 524 IV. Metabolite and cell activity responses to salt stress 527 V. Conclusions and perspectives 532 Acknowledgements 533 References 533 SUMMARY: Excess soluble salts in soil (saline soils) are harmful to most plants. Salt imposes osmotic, ionic, and secondary stresses on plants. Over the past two decades, many determinants of salt tolerance and their regulatory mechanisms have been identified and characterized using molecular genetics and genomics approaches. This review describes recent progress in deciphering the mechanisms controlling ion homeostasis, cell activity responses, and epigenetic regulation in plants under salt stress. Finally, we highlight research areas that require further research to reveal new determinants of salt tolerance in plants.