RNA-Seq reveals new DELLA targets and regulation in transgenic GA-insensitive grapevines

Authors: ARRO, JIE - Oak Ridge Institute For Science And Education (ORISE); Yang, Yingzhen; SONG, GUO-QING - Michigan State University; Zhong, Gan-Yuan

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2019
Publication Date: 2/18/2019
Citation: Arro, J., Yang, Y., Song, G., Zhong, G. 2019. RNA-Seq reveals new DELLA targets and regulation in transgenic GA-insensitive grapevines. Biomed Central (BMC) Plant Biology. 9(1):80. https://doi.org/10.1186/s12870-019-1675-4.
DOI: https://doi.org/10.1186/s12870-019-1675-4

Interpretive Summary: Flowering is an important attribute of plants. Some plants can flower under certain growing conditions while some other don’t. Biology of flowering is complex and much of our knowledge in this area has been obtained from the studies of annual species. While we know that flowering induction is different between annual and perennial species, we know very little about the molecular processes and genes which are responsible for the difference. In this study, we created transgenic grapevines which carried a mutated gene, Vvgai1, which mimicked a natural grapevine mutant with a continuous flowering attribute. We examined the behaviors of gene expression using a method called as “RNA-Seq” in leaf, shoot, and root tissues and compared them with a control. We found that the expression behaviors of many genes were affected by the introduced Vvgai1, which was expected because a Vvgai1-like gene has been found to play many critical roles in plant growth and development, including flowering induction, from many previous studies in annual species. However, we also found some genes with interesting and unique expression patterns which contrasted with the expression patterns of their counterparts in annual species. Among them are several flowering induction related genes. Our work provides insights into how Vvgai1 regulates grapevine development and growth, especially in relation to flowering, and fills some critical knowledge gaps in this important research area between annual and perennial species.

Technical Abstract: To understand GA-DELLA signaling in perennial species, we created GA-insensitive transgenic grapevines carrying a DELLA mutant allele (Vvgai1) in the Vitis vinifera ‘Thompson Seedless’ grape and studied their RNA-Seq expression profiles. Ten Agrobacterium-based transgenic lines were created. RNA-Seq profiles were analyzed from leaf, shoot and root tissues of a non-transgenic control and five selected transgenic lines. We identified and analyzed a set of differentially expressed genes (DEGs) which were highly correlated with the Vvgai1 expression among the transgenic lines. Transgenic lines were dwarf with other typical DELLA mutant phenotypes tightly correlated with the levels of Vvgai1 expression. The DEGs identified in this study were involved in diverse biological processes; many showed strong tissue specificity; and about 30% them carried a DELLA motif. We confirmed many previous DELLA study results in annual species, but also revealed new DELLA targets and responses in grapevine, including the roles of homeodomain transcription factors and their motifs as potential co-regulators with DELLA in controlling the development of grapevine vegetative and reproductive meristems. We further discovered unexpected expression patterns of key flowering induction genes VvCO, VvCO1, VvSVP and VvTFL1 which offers a likely explanation of the different GA-facilitated flowering behaviors between annual and perennial species. This work provides a new insight into the divergence between annual and perennial species in GA-DELLA signaling, especially in the flowering induction pathways.