Exogenous spraying of IAA improved the efficiency of microspore embryogenesis in wucai (Brassica campestris L.) by affecting the balance of endogenous hormones, energy metabolism and cell wall metabolism

Abstract Background : Spraying indoleacetic acid (IAA) on the buds of Wucai ( Brassica campestris L.) can increase the incidence of isolated microspore embryogenesis, but the mechanism of increasing microspore development remains unclear. Results : The statistics of isolated microspore embryogenesis showed that spraying100 mg . L -1 IAA (purity 99%) to the bud was the optimal concentration for inducing isolated microspore embryogenesis in B. campestris L. Microscopic observation showed that IAA treatment accelerated the development process of microspores. In addition, the contents of amino acids, soluble total sugar, protein, and starch were significantly increased, and the dynamic balance between hormones was changed due to the change of endogenous hormone content. To explore the molecular mechanism of IAA affecting microspore embryogenesis, the mononuclear flower buds which were treated with IAA for 24h were selected and the mononuclear flower buds which were treated with the same dose of water at the same period were used as the control for transcriptome analysis. It was found that more DEGs was enriched in plant hormone synthesis and signal transduction pathways, pentose and glucuronic acid exchange pathway, and oxidative phosphorylation pathway, and most of them showed upregulation. These changes of DEGs broke the balance between endogenous plant hormones, initiated the generation of microspore embryos, accelerated the metabolism of the cell wall and the development of microspores. Conclusions : This study helped to clarify the mechanism of microspore embryogenesis by IAA spring and provided a basis for further research on the molecular mechanisms of microspore development and the selection of key genes.