Transcriptome variation along grapevine bud development

Abstract

Vegetative buds provide plants in temperate climates the ability to overcome adverse environmental conditions allowing growth and reproduction when conditions are favorable. Decisive developmental events take place within grapevine buds during growing seasons over two consecutive years. The first season, the shoot apical meristem within the bud differentiates all the basic elements of the shoot including development ofinflorescence primordia. These events practically end with bud dormancy. The second season, buds resume shoot growth together with flower initiation and development. We have monitored gene expression changes at eight time points along the bud annual cycle (two growing seasons). Principal Component Analysis (PCA) showed that rnain factors explaining global bud gene expression variation during the year were dorrnancy onset and release as well as stress responses. Functional categories enrichment analysis revealed in non dormant buds typical mechanisms of actively proliferating and growing cells whereas in dormant ones, transcripts were more related to stress response pathways. Differential expression analyses indicated that majar transcriptional changes were associated to para/endodormancy, endo/ecodormancy and ecodormancy/bud break transitions. Transcripts encoding key regulators of reproductive development gathered into three majar expression clusters related to specific developmental processes: i) flowering induction, ii) flower meristem initiation and flower organ development and iii) dormancy maintenance. This work pro vides a global view of majar transcriptional changes taking place along bud development in grapevine, highlighting molecular and biological functions involved in the rnain events of bud development. As reported in other woody species, the results suggest that genes regulating flowering could also be involved in dormancy regulatory pathways in grapevine.