Comparative transcriptome profiling of Allium sativum L. (garlic) plantlet in vitro during hyperhydricity

Hyperhydricity (HH) is considered to be one of the most serious problems in plant tissue culture and there is no effective solution to solve and control HH, especially for garlic. The most important reason is that the underlying molecular mechanism of hyperhydricity is largely unknown. In order to investigate the HH-related genes and pathways, Illumina sequencing technology was used to catalog global gene expression profiles in two treatments (0.3%agar and 0.7%agar) of endogenesis H₂O₂ at different time (treat 0h, 4h, 24h and 8d). Results found that 0.3%agar will induced the ROS burst. During the process of HH, low concentration of Hydrogen peroxide (H₂O₂) plays as a signal substance which can alleviate HH and high concentration of H₂O₂ plays as a poisonous material which can aggravate hyperhydricity. In the results of assembly, 101298 unigenes are detected, 45133 unigenes are annotation and 42339 CDS are mapped to protein database. Genes relating to biosynthesis, transport, and response of phytohormones, such as auxin, cytokinin, and ethylene, were differentially expressed in the ROS burst stages. Differential expression of 30 genes identified by sequencing in 8 different treatments during the process of HH was independently confirmed by quantitative real-time-polymerase chain reaction. We found that the HH and associated processes are highly ROS demanding. Our study is the first study about the HH-related genes, and will sheds light on the transcriptional changes that accompany HH and aid in controlling method for HH.