Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2001
Publication Date: N/A
Interpretive Summary: Premature shedding of flowers, fruits and pods reduces the potential yield of many crops. Moreover, mechanical harvesting of fruit is impeded by the non-uniform ripening and loosening of the fruit. The plant hormone ethylene is involved in the induction of ripening, senescence, and separation of flowers, fruit and leaves from the parent plant. To increase the yield and efficiency of harvesting plant parts we have undertaken a project to identify the sensory mechanisms involved in ethylene perception. We reduced the expression of one of the ethylene sensor proteins in tomato and observed that it caused a delay in organ separation and cell size but had no effect on fruit ripening. We conclude that tomato uses different ethylene sensors depending on the environmental conditions and developmental stage of the plant. This information will be used by other researchers and plant engineers studying ethylene action in agriculturally important crops.
Stable transformation of tomato plants with a construct containing the antisense sequence for the receiver domain and 3' untranslated portion of the tomato ethylene receptor (LeETR1) under the control of an enhanced CaMV 35S promoter, resulted in some expected and unexpected phenotypes. In addition to reduced LeETR1 transcript levels, the two most consistently observed phenotypes in the transgenic lines were delayed abscission and reduced plant size. Altered epinastic responses were also observed in several of the transgenic lines. Fruit coloration and softening were essentially unaffected, and all the seedlings from first generation seed displayed a normal triple response to ethylene. Two independent lines with a single copy of the transgene and reduced LeETR1 transcript accumulation were selected for detailed analysis of phenotype segregation and expression in second-generation (R1) plants. Delayed abscission, shorter internode length and reduced auxin movement all segregated with the transgene and correlated with the degree of reduced LeETR1 transcript accumulation. No significant differences were noted for fruit coloration or fruit softening on R1 plants and all seedlings from R1 and R2 seed displayed a normal triple response. LeETR2 transcript accumulation was only slightly reduced in the R1 plants compared to azygous plants and LeETR3 (NR) transcript levels appeared to be unaffected by the transgene.