Jasmonic acid biosynthetic genes TgLOX4 and TgLOX5 are involved in daughter bulb development in tulip (Tulipa gesneriana)

Tulip bulbs are modified underground stems that originate from axillary meristems of mother bulb scales. Hormones, including jasmonic acids (JAs), play key roles in the regulation of tulip bulb development. Here, we compared variations in daughter bulb development through transcriptomic profiling analysis and characterized the functions of JA biosynthesis-related genes during daughter bulb enlargement. The results showed that tulip cultivars exhibited contrasting bulb size variations. Transcriptomic analyses revealed that genes involved in plant hormones and development, including the two lipoxygenase genes TgLOX4 and TgLOX5, showed significant changes in expression following tulip bulb growth. Ectopic overexpression of TgLOX4 and TgLOX5 in Arabidopsis enhanced endogenous JA content, improved plant growth, and increased lateral root numbers. Silencing of these two genes in tulip repressed the growth of daughter bulbs. Furthermore, exogenous JA treatment promoted tulip bulb growth, whereas the JA biosynthesis inhibitor sodium diethyldithiocarbamate (DIECA) inhibited this process. This study offers supporting evidence for the involvement of tulip TgLOX4 and TgLOX5 in the regulation of daughter bulb growth and development.