Ion measurements by X-ray microanalysis in unfixed, frozen, hydrated plant cells of species differing in salt tolerance

This obituary highlights the careers and contributions of two eminent plant physiologists. Emeritus Professor Reinhard Van Steveninck (1928–2017) was educated at Wageningen and London University. He joined the Department of Scientific and Industrial Research (DSIR), New Zealand, and achieved early recognition for his publications on abscission and mechanisms of salt uptake of plants. He was appointed Professor of Agriculture (Plant/Soil Science) at La Trobe University in 1976. He expanded his research into salinity tolerance of lupins and the ultrastructural localisation of ions using X-ray microprobe analysis. He was a good teacher and nurtured and trained many researchers in this area. He was a recognised expert in using a combination of ultrastructural techniques to study the movement of ions within plant cells and across tissues. His publications include book chapters on plant physiology, as well as a major review on the ‘washing’ or ‘ageing’ phenomenon in plant tissues. He was an active member and President of the Australian Society of Plant Physiologists. Margaret Van Steveninck (1931–2017) worked as a Research Assistant at Adelaide University and subsequently as a Demonstrator and Senior Demonstrator in Botany at Queensland and La Trobe University. Her plant physiology research with her husband resulted in numerous joint publications including a chapter on microanalysis in ‘Electron microscopy of plant cells’.

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Comparative Functional Analysis of Class II Potassium Transporters, SvHKT2;1, SvHKT2;2, and HvHKT2;1, on Ionic Transport and Salt Tolerance in Transgenic Arabidopsis

Plants ◽

10.3390/plants9060786 ◽

2020 ◽

Vol 9 (6) ◽

pp. 786

Author(s):

Yuichi Tada ◽

Aki Ohnuma

Keyword(s):

Salt Tolerance ◽

Transport Properties ◽

Plant Cells ◽

Ionic Transport ◽

Class Ii ◽

Phloem Sap ◽

Over Expression ◽

Potassium Transporters ◽

Transgenic Lines ◽

Reduced Salt

Class II high-affinity potassium transporters (HKT2s) mediate Na+–K+ cotransport and Na+/K+ homeostasis under K+-starved or saline conditions. Their functions have been studied in yeast and X. laevis oocytes; however, little is known about their respective properties in plant cells. In this study, we characterized the Na+ and K+ transport properties of SvHKT2;1, SvHKT2;2 and HvHKT2;1 in Arabidopsis under different ionic conditions. The differences were detected in shoot K+ accumulation and root K+ uptake under salt stress conditions, K+ accumulation in roots and phloem sap under K+-starved conditions, and shoot and root Na+ accumulation under K+-starved conditions among the HKT2s transgenic lines and WT plants. These results indicate the diverse ionic transport properties of these HKT2s in plant cells, which could not be detected using yeast or X. laevis oocytes. Furthermore, Arabidopsis expressing HKT2s showed reduced salt tolerance, while over-expression of HvHKT2;1 in barley, which has the ability to sequestrate Na+, showed enhanced salt tolerance by accumulating Na+ in the shoots. These results suggest that the coordinated enhancement of Na+ accumulation and sequestration mechanisms in shoots could be a promising strategy to confer salt tolerance to glycophytes.

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