Effects Of Over-expression Of Two Endogenous Phytochrome Genes On Plant Type In Maize

Plants are regulated by the light in its life cycle including seed germination, hypocotyl elongation growth, development of root, stem and leaf. Light not only provides energy source for plant growth and development, but also as regulates many physilogical and biochemical processes as a signal, especially relative to photomorphogenesis. There are three types of the photoreceptors in plant:phytochrome, cryptochrome and phototropin. The phytochromes are the best-characterized family of photoreceptors, regulating gene expression in various stages of plant growth and development.Shade avoidance of plant affects crop productivity at high density. The encoding genes of phytochromes A (PhyA) and B (PhyB) are relative to shade avoidance of plant. In this work, the encoding genes of maize phytochromes, and used to transforme maize for over-expression, to explore the probability to improve plant type and shade avoidance by the favorable change of light signal pathway. The results are:1. The over-expression vector of maize phytochrome A gene ZmPhyA2 was used to transforme embyronic calli of maize inbred "18-599R" by the mediation of Agrobacterium. The positive calli were screened on medium with blufosinate of 1.5,2.0 and 2.5 mg/L for three times, and regenerated for plantlets on differentiation medium. Four positive plantlets were indentified by PCR amplification from the 59 regenerated plantlets.2. The inheritance of the phytochrome genes in transgenic offsprings was analyzed by specific PCR amplification of T5 and T6 lines transformed by ZmPhyAl and ZmPhyA2, The results showed that the percentages of the positive individual plants were 50%and 45.7% in the T5 lines, and 76.2% and 75.0% in the T6 lines, indicating the increasing positive rate of the transgenic plants and the stable inheritance of the transformed genes.3. The T7 lines transformed by the ZmPhyAl and ZmPhyBl genes, as well as their non-transformed parent line 18-599R, were planted with densities 52,500,67,500 and 75,000 plant/hm2 in a randomized block design with three replicates. The plant type traits (plant height, ear height, leaf length, leaf width and leaf angle) were investigated. Statistical analysis showed that the plant height, ear height and leaf length of the T7 line transformed by the ZmPhyA1 gene increased greatly significantly, while the leaf angledecreased significantly, and leaf width was non-significantly different, in comparison to the control line 18-599R. The plant height, leaf length and leaf width of the T7 line transformed by the ZmPhyBl gene increased greatly significantly or significantly, while the difference of ear height and leaf angle was non-significant, in comparison to the control line 18-599R. Under the high density of 75,000 plant/hm2 particularly, the leaf angle of the transgenic lines decreased greatly significantly in comparison to the control line 18-599R.These results indicates that over-expression of the phytochrome genes have a significant impact on the maize plant type. This strategy can be utilized in maize improvement for plant type to breed maize varieties in adaptation to rational close planting.