Hydrogen peroxide and nitric oxide promote reproductive growth in Litchi chinensis

Vegetative growth and reproductive growth strongly competes with each other during panicle development in litchi (Litchi chinensis Sonn.). We herein investigated the roles of hydrogen peroxide and nitric oxide in the competition between growth of rudimentary leaves and panicle development. The results show that the chilling-induced flowering increased H2O2 and NO contents in the mixed buds. Treatments with sodium nitroprusside (SNP), the NO donor, and methyl viologen dichloride hydrate (MV), the superoxide generator, increased NO and H2O2 contents in the mixed buds. MV and SNP treatments promoted abscission of rudimentary leaves and encouraged panicle development before or at the stage of panicle emergence. The nitric oxide synthase inhibitor N (omega) -nitro-L-arginine methyl ester (L-NAME) and the H2O2 trapper dimethylthiourea (DMTU) inhibited a chilling-induced flowering. SNP promoted the expression of litchi LEAFY homolog (LcLFY). These promotive effects were suppressed by the NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl3-oxide (PTIO) and the H2O2 trapper, DMTU. The results suggest that H2O2 and NO promote reproductive growth by inhibiting the growth of rudimentary leaves as well as by promoting the expression of the flower related gene, LcLFY.