Naturally occurring cinnamic acids (CA) exist in both
trans- and cis-isoforms. UV-light
irradiation of trans-CA is able to produce
cis-CA. cis-CA was found to
possess auxin-like activity before. In contrast, the vapor of
cis-CA induced an epinastic response in tomato plants
just as ethylene does. Given the existence of a double bond in and the gaseous
nature of cis-CA, we suspected that
cis-CA might also function as an ethylene-like compound.
To distinguish between these possibilities, we selected an ethylene
perception-deficient tomato plant, Never-ripe
(Nr), and an ethylene biosynthesis-deficient tomato
plant, A11. Not only did the vapor of cis-CA fail to
trigger A11 tomato fruit ripening but it also delayed the ripening of banana
fruit. Moreover, the vapor of cis-CA induced epinasty
and the ‘triple response’ in both the wild type and
Nr tomato plants, indicating that the vapor of
cis-CA does not act via an ethylene receptor-dependent
pathway. Furthermore, the vapor of cis-CA inhibited the
negative gravitropic response of stems of both etiolated
Nr seedlings and young plants, whereas ethylene had
little effect on the negative gravitropism of the Nr
plants. These results support the conclusion that the action sites of the
vapor of cis-CA and ethylene are fundamentally
different.
Roles of SlETR7, a newly discovered ethylene receptor, in tomato plant and fruit development
