Methylome and Transcriptome Analysis Reveals Differences in Callus Development and Plantlet Regeneration Capacity Between Two Eucalyptus Species

<i>Eucalyptus</i> is a highly diverse genus of the <i>Myrtaceae</i> family that is planted worldwide. Many changes occur during callus development, an important process during in vitro plant regeneration. In this study, we conducted methylome and transcriptome analyses to reveal such changes. The results showed that differentially expressed genes between <i>E. camaldulensis</i> (voucher ID: c0009; high embryogenic potential) and <i>E. grandis</i> × <i>urophylla</i> (voucher ID: j0017; low embryogenic potential) during callus development were enriched in plant hormone signal transduction and MAPK (Mitogen-activated protein kinase) signaling pathways. qRT-PCR analysis showed <i>AHP</i>, <i>BAK1</i>, <i>BSK</i>, <i>CRE1</i>, <i>GID1</i>, <i>MKS1</i>, <i>PR-1</i>, <i>PYL</i>, <i>RbohD</i>, and <i>TCH4</i> could be involved in the callus development and plantlet regeneration capacity. The differences observed in regenerative potential during callus maturation between the two species under study provide a reliable molecular basis for the study of <i>Eucalyptus</i> regeneration mechanisms.