Effect of short-term temperature stress on fruit set and the expression of an auxin reporter gene and auxin synthesis genes in tomato

Abstract

• Effect of short-term temperature stress was evaluated during 5 days before anthesis. • Auxin-related factors were investigated using Micro-Tom as a model system. • DR5::GUS expression under high temperature was inhibited with the fruit development. • Fruit set and DR5::GUS expression were not inhibited under low-temperature stress. • The expression of ToFZY for auxin synthesis were affected by high-temperature stress. Poor fruit set and growth are known to be caused by temperature stress in tomato cultivation. We focused on the effect of short-term temperature stress on each day during the five days before anthesis. The relationship between temperature stress and auxin-related factors was investigated using an experimental tomato cultivar, Micro-Tom expressing the auxin reporter DR5::GUS as a model system. While DR5::GUS expression in the control plants increased in ovaries and transferred to peduncles during the later developmental stages, that under high-temperature stress was not detected or very low. Some smaller fruit grew even under high-temperature stress probably due to the low level of DR5::GUS expression. Therefore, it was suggested that temporary high-temperature stress at any stage in this study affected the localization of auxin to ovaries and peduncles, and further affected fruit set and growth. By contrast, no decreased fruit set was observed with some delay and recovery of fruit growth under low-temperature stress, and this corresponded to the levels of DR5::GUS expression. The expression of GUS with the promoter of the tomato PIN gene, which is involved in the auxin transport, was not affected by high-temperature stress. On the other hand, the expression of ToFZY genes involved in auxin synthesis were affected by temperature stress, suggesting a part of the mechanism of the decrease in DR5::GUS expression under high-temperature stress.