Mechanism Of Light Environment Influencing The Expression Of Correlated Genes In Biosynthesis Pathway Of Anthocyanin

Two cultivars of Brassica campestris L. ssp. rapifera, light-independent 'Akamaru' turnip and light-dependent 'Tsuda' turnip, were used as test material in this experiment. The expression patterns of PAL, CHS, CHI, AS, PHYA, COP1, CIP7 and HY5 were analyzed by Northern Hybridization. PAL, CHS, CHI and AS are the principal structural genes correlated with anthocyanin biosynthesis in anthocyanin biosynthesis pathway; PHYA, COP1, CIP7 and HY5 are the genes correlated with light signal transmission in anthocyanin biosynthesis pathway. Total RNA samples used in Northern blotting were extracted from the light-exposed and light-interrupted cortex tissue of tuberous root of the two turnip cultivars. The probes of CHS, PHYA, COP1, CIP7 and HY5 genes were synthesized by total RNA extracted from the cortex tissue of tuberous root of turnip, the probes of PAL and CHI were synthesized by total RNA extracted from the petal tissue of Eustoma, and the probes of AS were synthesized by total RNA extracted from the fruit tissue of strawberry. The content of anthocyanin and main sugars (fructose, glucose, sucrose and maltose) in the light-exposed and light-interrupted samples of the two turnip cultivars were analyzed by HPLC. The CHS gene which is obvious correlated with anthocyanin accumulation was cloned as well.The results are as follows:1. A large quantity of anthocyanin was synthesized in both of the light-exposed and light-interrupted cortex tissue of tuberous root of light-independent 'Akamaru' turnip, but only in the light-exposed cortex tissue of tuberous root of light-dependent 'Tsuda' turnip. There was almost no anthocyanin synthesized in light-interrupted cortex tissue of tuberous root of light-independent 'Tsuda' turnip.2. Glucose' s content was more abundant than that of fructose, sucrose and maltose in tuberous root and leaf tissues of the two cultivars, but there were no obvious correlations between glucose accumulation and anthocyanin biosynthesis. The content of the four sugars in tuberous tissue was higher than that in other tissues of tuberous root of the two cultivars. There were little sugars in leaf tissues. The content of fructose in the light-exposed cortex tissue of tuberous root of 'Tsuda' turnip was obviously higher than that in light-interrupted cortex tissue. The content of fructose wasincreased gradually along with the prolongation of light-exposing time and stabled at high content level. There were no evident changes for the content of other three sugars after light-exposing.3. There was distinct difference for the expression patterns of CHS gene in light-exposed and light-interrupted tissues of light-dependent 'Tsuda' turnip. Light-exposing the tuberous root of 'Tsuda' turnip grown under dark condition, the expression quantity of CHS gene was gradually increased along with the prolongation of light-exposing time. This indicated that the expression of CHS gene was induced by light, and the expression quantity was positively correlated with accumulation of anthocyanin. There was no distinct difference for the expression patterns of CHS gene in light-exposed and light-interrupted tissues of light-independent 'Akamaru' turnip. Therefore, we think that the expression of CHS gene played a key role in accumulation of anthocyanin in light-dependent materials. The expression quantity of AS gene was correlated with synthesis quantity of anthocyanin. The expression of AS gene was induced by light in light-dependent 'Tsuda' turnip. The expression of light signal transmission factor PHYA is different in the two cultivars. PHYA gene expressed only in light-interrupted part of light-dependent 'Tsuda' turnip. In the two cultivars, COP1 and HY5 expressed both in the light-exposed and light-interrupted parts of the two cultivars, but the expression quantity in light-exposed parts was higher than that in light-interrupted parts. The expression of CIP7 had no obvious difference in light-exposed and light-interrupted parts of two cultivars.