Table_4_Transcriptome Profiling Predicts New Genes to Promote Maize Callus Formation and Transformation.xlsx

Maize transformation is highly based on the formation of embryonic callus, which is mainly derived from scutellum cells of the immature maize embryo. However, only a few genes involved in callus induction have been identified in maize. To reveal the potential genes involved in the callus induction of maize, we carried out a high-throughput RNA sequencing on embryos that were cultured for 0, 1, 2, 4, 6, and 8 days, respectively, on a medium containing or lacking 2,4-dichlorophenoxyacetic acid. In total, 7,525 genes were found to be induced by 2,4-dichlorophenoxyacetic acid and categorized into eight clusters, with clusters 2 and 3 showing an increasing trend related to signal transmission, signal transduction, iron ion binding, and heme binding. Among the induced genes, 659 transcription factors belong to 51 families. An AP2 transcription factors, ZmBBM2, was dramatically and rapidly induced by auxin and further characterization showed that overexpression of ZmBBM2 can promote callus induction and proliferation in three inbred maize lines. Therefore, our comprehensive analyses provide some insight into the early molecular regulations during callus induction and are useful for further identification of the regulators governing callus formation.

玉米遗传转化高度依赖胚性愈伤组织的形成，而胚性愈伤组织主要源自未成熟玉米胚的盾片细胞。然而，目前在玉米中仅鉴定出少量参与愈伤组织诱导的基因。为揭示参与玉米愈伤组织诱导的潜在基因，我们对分别在含有或不含2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid）的培养基中培养0、1、2、4、6和8天的玉米胚开展了高通量RNA测序（RNA sequencing）。最终共鉴定得到7525个受2,4-二氯苯氧乙酸诱导的基因，并将其划分为8个表达簇，其中簇2和簇3呈现表达上调趋势，关联的基因功能包括信号传递、信号转导、铁离子结合与血红素结合。在上述诱导基因中，共有659个转录因子（transcription factor）隶属于51个基因家族。其中AP2类转录因子ZmBBM2可被生长素快速且显著诱导；进一步功能表征结果显示，在三个玉米自交系中过表达ZmBBM2能够促进愈伤组织的诱导与增殖。综上，本研究的综合分析为愈伤组织诱导早期的分子调控机制提供了新的见解，同时可为后续鉴定调控愈伤组织形成的关键调控因子提供参考依据。