Transcriptional Regulation Of Ethylene Biosynthesis By SlEIL In Tomato

Tomato (Solarium lycopersicum Mill.) were chosen for researches on regulation mechanisms of ethylene biosynthesis by SIEIL (transcription factors of ethylene signal transduction), using gene expression, gene-gene interaction and SIEIL1 antisense transgenic materials. The main results are as follows:1. Tissue-specific analysis indicated that SIACS2, SlACS4 and SlACO1 strongly expressed in tomato fruit, SlACS1, SlACS3, SlACS8, SlACO2, SlACO3 and SlACO4 were abundant in flowers, SlACO5 had the relative higher expressions in leaves, while SlACS6 and SlACS7 constantly expressed in various tomato tissues. Some SIACS and SlACO genes were weakly expressed in specific tissues, such as transcripts abudance of SlACO6 were relative lower in stems than the other tissues, SIACS5 was not dectectable in fruit.2. In order to analyze temporal expression patterns of SlEIL, SIACS and SlACO, tomato fruit at four different ripening stages, including MG(Mature Green), BR(Breaker), PK(Pink) and RR(Red), were collected. Physiological measurements indicated that increasing of color index, ethylene production, softening, in parallel with fruit maturity. Among the SIACS genes, SlACS2 and SlACS4 had remarkable increasement during fruit ripening, enhanced expression of SIACS8 was observed since PK stage, while SlACS1, SlACS3, SlACS6 and SIACS7 remained constant. SIACO genes also exhibited different expression patterns during fruit ripening, with expression of SlACO1, SlACO2 and SlACO3 were increased during fruit ripening, transcripts of SlACO5 was accumulated in RR fruit, expression of SlACO6 had a slight increament in BR, while SlACO4 constitutively expressed. Four SlEIL gene were relative more constant, compared with SlACS and SIACO genes, with SlEIL1 had a slight accumulation in BR fruit and SIEIL4 expression exhited increasing trends during fruit ripening.3. With attempt to investigate the regulatory roles of SIEIL on ethylene biosynthesis, antisense transgenic tomato (1AS-2) was chosen. Transgenic seedlings had the lower ethylene production than that of WT seedlings, after 100 μl/L ethylene treatment (18 h), while in tomato fruit, ethylene production had no significant difference between 1 AS-2 and wide type, both at BR and BR+7d. Further experiment confirmed transgenic plants, as the four SlEIL genes were all suppressed in 1AS-2 seedlings. Meanwhile, expression of SlACS1, SlACS3, SlACOS, SlACO4 and SlACO6 were significantly repressed in 1AS-2 seedlings, compared with WT seedlings. These results indicated that SlEIL genes may contribute ethylene biosynthesis in tomato seedling by regulation on above-mentioned specific isoforms.4. The transcriptional regulatory roles of SIEIL genes on the specific isoforms were further analyzed using dual-luciferase assay in tobacco leaves. The results indicated that SlEIL1-4 could stimulate the activity of the promoters of SlACS1, SlACO3 and SlACO4, but had the little effect on the promoters of SIACS6 and SlACO2. Taken together the ethylene production and genes expression in transgenic seedlings and the trans-activation experiments, the results indicated that SlEIL could regulate tomato seedlings ethylene production by interacting with specific SlACS and SIACO genes.