sas1, an Arabidopsis Mutant Overaccumulating Sodium in the Shoot, Shows Deficiency in the Control of the Root Radial Transport of Sodium

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American Society of Plant Physiologists

RESUMO

A recessive mutation of Arabidopsis designated sas1 (for sodium overaccumulation in shoot) that was mapped to the bottom of chromosome III resulted in a two- to sevenfold overaccumulation of Na+ in shoots compared with wild-type plants. sas1 is a pleiotropic mutation that also caused severe growth reduction. The impact of NaCl stress on growth was similar for sas1 and wild-type plants; however, with regard to survival, sas1 plants displayed increased sensitivity to NaCl and LiCl treatments compared with wild-type plants. sas1 mutants overaccumulated Na+ and its toxic structural analog Li+, but not K+, Mg2+, or Ca2+. Sodium accumulated preferentially over K+ in a similar manner for sas1 and wild-type plants. Sodium overaccumulation occurred in all of the aerial organs of intact sas1 plants but not in roots. Sodium-treated leaf fragments or calli displayed similar Na+ accumulation levels for sas1 and wild-type tissues. This suggested that the sas1 mutation impaired Na+ long-distance transport from roots to shoots. The transpiration stream was similar in sas1 and wild-type plants, whereas the Na+ concentration in the xylem sap of sas1 plants was 5.5-fold higher than that of wild-type plants. These results suggest that the sas1 mutation disrupts control of the radial transport of Na+ from the soil solution to the xylem vessels.

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