Poster: Nutrient Biology

Abs # 402: Isolation and characterization of tomato mutants altered in the response to phosphate-deficient conditions

Presenter:	Xu, Guohua , guohua.xu@weizmann.ac.il
Authors	Xu, Guohua  (A)   Chague, Veronique  (A)   Bessudo, Cathy  (A)   Levy, Avraham  (A)   Silber, Avner  (B)
Affiliations:	(A): Plant Science Dept., Weizmann Institute of Science (B): Soil & Water Institute, Agricultural Research Organization

In order to study the genetic and molecular regulation of P acquisition we have isolated tomato mutants (Lycopersicon esculentum), altered in response to Pi-deficient conditions. Phosphate efficient mutants were obtained upon screening of a M2 population of fast-neutron-irradiated seeds from cultivar M82, using a hydroponics system. Five lines were identified as resistant to extremely low P (0.025-mM) supply condition. Earliest visible growing difference appeared just two weeks after emergence between the seedlings of the M2 mutants and wild type. Under these conditions, the WT plants showed severe P deficiency symptoms. In three lines out of these lines, low-P resistance was confirmed in the next, M3, generation. The total fresh weight of the selected M3 lines supplied with 0.1 mM P, was 384; 389 and 460 g/plant and the P content in the shoot of the plants was 2.03; 2.27 and 2.21 g/kg dry weight respectively. The concentrations of other nutrients were not affected in the mutants. Under these conditions the wild type produced only 296-g fresh weight/plant and contained 1.49-g/kg of P. Under normal P concentrations (1 mM P) there was no significant difference in biomass yield and shoot P content between the wild type and mutants. Northern blot analysis showed that the P-deficiency induced the expression of high affinity transporter LePT2 specifically in roots and of LePT1 both in roots and leaves, but not of LePT3 (a new member of tomato P transporter) in both the mutants and the wild type. In addition, we isolated a homozygote LePT3 mutant in the cultivar Micro-Tom, by Ds-transposon tagging. This LePT3 mutant was more sensitive to the Pi-starvation than the wild type.