Reduced de-etiolation of hypocotyl growth in a tomato mutant is associated with hypersensitivity to, and high endogenous levels of, abscisic acid.
A recessive single gene mutant, 7B-1, in tomato was originally selected for its photoperiod-dependent male sterility. The 7B-1 mutant also has some pleiotropic effects including reduced light-induced inhibition, i.e. de-etiolation, of the hypocotyl in long days (LD), increased seed size and weight, and reduced transpiration rate. These traits led us to investigate the sensitivity of 7B-1 to exogenous hormones and the interaction of these responses with daylength. In LD, but not in short days (SD), 7B-1 was more sensitive than wild-type (WT) to exogenous abscisic acid (ABA) for inhibition of seed germination, root elongation and transpiration rate. 7B-1 mutant also exhibited reduced responses to exogenous gibberellin (GA(3)) for hypocotyl elongation, and to inhibitors of GA biosynthesis for seed germination and root and hypocotyl elongation. 7B-1 hypocotyls contained a higher level of endogenous ABA than WT in both photoperiods, although ABA levels were higher in LD than in SD. In contrast, growth-active GAs, i.e. GA(1), GA(3) and GA(4), and IAA were low in the mutant hypocotyls. The 7B-1 mutant appears to be an ABA-overproducer, and the photoperiod-regulated ABA levels may be responsible for the hypersensitivity of the mutant to exogenous ABA.
Fellner
M
M
Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.
Zhang
R
R
Pharis
R P
RP
Sawhney
V K
VK
D000040:Abscisic Acid / Q000378:metabolism*; D005808:Genes, Recessive; D018525:Germination; D005875:Gibberellins / Q000494:pharmacology; D018546:Hypocotyl / Q000254:growth & development*; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017440:Photoperiod; D018517:Plant Roots / Q000254:growth & development; D011728:Pyridones / Q000494:pharmacology; D012639:Seeds / Q000254:growth & development
D005875:Gibberellins; D011728:Pyridones; C013351:fluridone; D000040:Abscisic Acid