Deficiency of GDP-l-galactose phosphorylase, an enzyme required for ascorbic acid synthesis, reduces tomato fruit yield

ALEGRE, MATÍAS L.; STEELHEART, CHARLOTTE; BALDET, PIERRE; ROTHAN, CHRISTOPHE; JUST, DANIEL; OKABE, YOSHIHIRO; EZURA, HIROSHI; SMIRNOFF, NICHOLAS; GERGOFF GROZEFF, GUSTAVO E.; BARTOLI, CARLOS G.

PLANTA

SPRINGER

Lugar: Berlin; Año: 2020 vol. 251

0032-0935

Reduced GDP-l-galactose phosphorylase expression and deficiency of ascorbic acid content lead to decreased fruitset and yield in tomato plants. GDP-l-galactose phosphorylase (GGP) catalyzes the first step committed to ascorbic acid synthesis.The participation of GDP-l-galactose phosphorylase and ascorbate in tomato fruit production and quality was studiedin this work using two SlGGP1 deficient EMS Micro-Tom mutants. The SlGGP1 mutants display decreased concentrationsof ascorbate in roots, leaves, flowers, and fruit. The initiation of anthesis is delayed in ggp1 plants but the number of flowersis similar to wild type. The number of fruits is reduced in ggp1 mutants with an increased individual weight. However, thewhole fruit biomass accumulation is reduced in both mutant lines. Fruits of the ggp1 plants produce more ethylene and showhigher firmness and soluble solids content than the wild type after the breaker stage. Leaf CO2uptake decreases about 50% inboth ggp1 mutants at saturating light conditions; however, O2production in an enriched CO2atmosphere is only 19% higherin wild type leaves. Leaf conductance that is largely reduced in both mutants may be the main limitation for photosynthesis.Sink-source assays and hormone concentration were measured to determine restrictions to fruit yield. Manipulation of leafarea/fruit number relationship demonstrates that the number of fruits and not the provision of photoassimilates from thesource restricts biomass accumulation in the ggp1 lines. The lower gibberellins concentration measured in the flowers wouldcontribute to the lower fruit set, thus impacting in tomato yield. Taken as a whole these results demonstrate that ascorbatebiosynthetic pathway critically participates in tomato development and fruit production.