Abstract:

This work aimed to regulate the volatile components and major quality traits of tomato fruits by down-regulation
of the expression of lycopene β-cyclase (LYC-B) gene using antisense RNA interference technique. Purple tomato fruits were
transformed by injection of the plant expression vector containing two conserved sequences (801 and 301 bp, respectively)
of LYC-B gene. The transgenic plants were obtained kanamycin resistance screening, polymerase chain reaction and
quantification of LYC-B gene expression. The volatile substances and major quality traits of ripe tomato fruits were compared
between the transgenic and wild-type (WT) plants. The results showed that alcohols, aldehydes, ketones, esters and other
volatiles were detected in transgenic tomato fruits. Compared with the wild-type control, six new volatile compounds were
identified from the transgenic fruits, consisting of three aldehydes, two ketones, and one ester, and one compound belonging
to another chemical class was detected in the control rather than the transgenic fruits. In addition, the same relative content
of aldehydes was observed between both fruits, but the transgenic fruits showed decreased relative content of alcohols
and increased relative contents of ketones, esters and other compounds. The characteristic volatile compounds were also
increased, such as (E) 2-heptenal, 6-methyl 5-hepten-2-one, methyl salicylate and 2-isobutylthiazole, and lycopene increase
by 16.78% compared with the wild-type fruits. In addition, the contents of soluble solids, ascorbic acid and total acid
were also increased. On the other hand, the contents of β-carotene and total sugar were identical to those of the WT fruits.
Therefore, down-regulated expression of LYC-B gene by RNA interference can affect volatile substances and enhance the
contents of lycopene, soluble solids, ascorbic acid and total acid, thereby improving the nutritional quality of tomato fruits.

Key words: lycopene β-cyclase, volatile compounds, nutritional quality, RNA interference, Agrobacterium injection