engleski

Auxin homeostasis in tomato and Arabidopsis under heat stress

The steady increase in temperature causes worldwide losses in agriculture, therefore heat stress is a problem in many areas in the world. Tomatoes are a major horticultural crop worldwide. Their yields are maximized in climates with moderate temperatures, whereas high temperature exposure limits tomato flower development, fruit set, and thus productivity. Experimental evidence indicates that reduced fruit set at high temperatures results from inhibited pollen development, anther release, and pollen viability reduction correlating with altered metabolism of the plant hormone auxin. We have therefore set out to analyze the auxin metabolome and transcriptome in tomato flower and fruit organs to identify candidates for alteration of auxin homeostasis. Among the strongly differentially regulated genes, four GH3 genes encoding auxin conjugate synthetases were specifically upregulated in male flower organs and gametophyte during flower development of tomato. We cloned these for heterologous expression in Escherichia coli to determine their in vitro activities. One highly regulated gene encoding an amino acid conjugate hydrolase has also been investigated in terms of activity. Since the generation of transgenic tomato plants is more time consuming than transformation of Arabidopsis, we have created transgenic lines overexpressing IAA amino acid conjugate hydrolases and GH3 genes from different sources and started to analyze these for possible heat stress tolerant phenotypes. Results from work with these transgenic plants will be presented.

auxin ; tomato ; Arabidopsis ; heat stress

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