KSEF RDE: Investigation of Regulatory Networks to Enhance Plant Regeneration by Somatic Embryogenesis

Transgenic plants to meet agricultural challenges require that a plant be regenerated from the transformed cell. This regeneration can be by organogenesis or somatic embryogenesis (SE), but many crops or desirable cultivars are difficult to regenerate. Soybean is one of the most important crop plants for protein, oil, and meal for animal feed, but transformation remains challenging. Transformation efficiency is positively correlated with competence for SE of different soybean cultivars. SE is poorly understood, even though it is a fundamental biological question concerning plant totipotency, and a model for zygotic processes in the seed. Seeds are essential to humans and constitute 70% of our diet directly. GmAGL15 is a soybean transcription factor (TF) that accumulates in developing seeds and that increases soybean SE when expressed by the constitutive 35S promoter. Preliminary work indicates that GmAGL15 may be influencing the competence of cells to respond to SE inductive treatment. The proposed experiments will examine how this TF promotes SE by constructing a gene regulatory network of direct and indirect target genes. RNA-seq would be performed at timepoints before and early in induction for SE, comparing control to 35S:GmAGL15 tissue. These datasets will allow genes responsive to increased TF accumulation and in response to SE induction to be identified. This data will be combined with ChIP-seq that will allow a determination of genome-wide binding sites for GmAGL15, both from the endogenous gene (normal GmAGL15 accumulation) and from 35S:GmAGL15 tissue (increased GmAGL15 accumulation) predisposed for SE. Combining the data allows one to determine direct from indirect targets. Understanding how GmAGL15 promotes SE can provide means to improve this process. For example we found 35S:GmAGL15 leads to increased ethylene production, and subsequently that addition of a precursor of ethylene to culture media could improve SE production.