THE BIOSYNTHESIC PATHWAYS FOR INDOLE-3-ACETIC ACID CHANGES DURING TOMATO FRUIT DEVELOPMENT

Authors: EPSTEIN, EPHRAIM - RUTGERS UNIVERSITY; COHEN, JERRY - UNIV OF MINNESOTA; Slovin, Janet

Submitted to: Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The plant hormone auxin is involved in a number of important processes in fruit tissues, including cell expansion, sensitivity to the ripening hormone ethylene, responses to stress, and control of fruit abscission, in addition to delaying fruit ripening. No information is available about how this hormone is made in fruits. Such information is necessary for manipulating the levels of this hormone so that we can more closely regulate these processes and obtain a more reliable harvest of quality fruit with good keeping characteristics. We therefore studied the processes in green and red tomato fruit that produce auxin. We showed for the first time that green fruit and red fruit use an entirely different pathway for production of the auxin within the fruit. This suggests that the regulation of auxin production also changes during fruit development. Using fruit from a non-ripening tomato mutant, we showed that this change is related to age or cessation of cell expansion, and not directly to other ripening events. This new information on how auxin is made at different times during fruit development has many potential uses for fruit crop improvement in processes important to both production and storage. This information should be of interest to molecular biologists, plant breeders, and others interested in development of improved plant varieties by biochemical, genetic or molecular techniques as well as producers, consumers and others interested in the benefits possible through genetic manipulation of fruit crop production.

Technical Abstract: Phytohormone metabolism during fruit ripening is critical to the control of this developmental process, yet we know little about pathways for the production of many of these signaling compounds. Using stable isotope labeling in both an in vitro aseptic tomato fruit culture system and detached greenhouse-grown tomato fruit, we have shown by mass spectral analysis that tomato uses the tryptophan-independent pathway to produce IAA from anthranilate or indole. We also show that there is a developmental switch from tryptophan utilization to tryptophan- independent production that occurs between mature green and red-ripe stages of fruit development. Moreover, this pathway switch does not appear to be associated with ripening per se in that fruit from neverripe tomato plants also utilize the tryptophan independent pathway.