Understanding grapevine responses to abscisic acid
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Authors
Rattanakon, Supakan
Issue Date
2015
Type
Dissertation
Language
Keywords
Abscisic acid , Grapevine , MYB121 , System biology
Alternative Title
Abstract
Abscisic acid (ABA) regulates various developmental processes and stress responses over both short (i.e. hours or days) and longer (i.e. months or seasons) time frames. To elucidate the transcriptional regulatory the early responses of grapevine (Vitis vinifera) responding to ABA, different organs of grape (berries, shoot tips, leaves, roots and cell cultures) were treated with 10 μM (S)-(+)-ABA for 2 h. NimbleGen whole genome microarrays for genes of Vitis vinifera were used to determine the effects of ABA on organ-specific mRNA expression patterns. Proteomic profiles were obtained from TMT labeling and label-free approaches.Transcriptomic analysis revealed 839 genes whose mRNA abundances varied significantly in different organs in response to ABA treatment. No single gene exhibited the same organ-specific changes in transcript abundance across all organs in response to ABA. The biochemical pathways affected by ABA were analyzed using the Cytoscape program with the BiNGO plug-in software. The results indicated that these genes were involved in several biological processes such as response to reactive oxygen species, response to light, and response to temperature stimulus. Protein amino acid phosphorylation process was significantly overrepresented in shoot tips and roots. ABA affected mRNA abundance of genes (CYP707As, UGTs, and PP2Cs) associated with ABA degradation, conjugation, and the ABA signaling pathway. ABA also significantly affected the expression of several transcription factors (e.g. AP2/ERF, MYC/MYB, and bZIP/AREB). The greatest number of significantly differentially expressed genes was observed in the roots followed by cell cultures, leaves, berries, and shoot tips, respectively. Each organ had a unique set of gene responses to ABA. Proteomics was performed using the same leaf samples from a previous transcriptomic analysis. In this study we investigate changes in protein abundance and phosphorylation of Cabernet Sauvignon grapevine leaves. Protein abundance was assessed by a label-free and isobaric-label method. Each identified common proteins, but also additional proteins not found with the other method. Overall, several thousand proteins were identified and several hundred were quantified. In addition, hundreds of phosphoproteins were identified. Tens of proteins were found to be affected in the leaf after the roots had been exposed to ABA for 2 h, more than half of them were phosphorylated proteins. Many phosphosites were confirmed and several new ones were identified. ABA increased the abundance of some proteins, but the majority of the proteins had their protein abundance decreased. Many of these proteins were involved in growth and plant organ development, including proteins involved in protein synthesis, photosynthesis, sugar and amino acid metabolism. Finally, MYB121, a candidate gene from transcriptomics, was study its functions. Expression of grapevine VviMYB121 had been found to be highly induced by ABA only in the roots treated with 10 μM (S)-(+)-ABA for 2 h. In order to understand the functions of MYB121, phenotype study of knockout mutants of atmyb121 under different stress conditions such as salt, ABA, and osmotic stress was performed. The mutant plants of atmyb121 showed that they had significantly more lateral root length under ABA and normal conditions, while atmyb121_2 had significantly lower primary root growth rate under normal, osmotic, and salt conditions compared to wild type. Moreover, the higher relative growth rate, and earlier flowering were found in atmyb121 mutant plants. The real-time quantitative PCR (qPCR) result of AtMYB121 indicates that AtMYB121 increase the relative expression in roots in time- and ABA concentration- dependent manner. In this study, we assigned a new role for AtMYB121 involved in ABA signaling and root growth and development.Overall, this study examined the short-term effects of ABA on different organs of grapevine using transcriptomic and proteomic approaches. The responses of each organ were unique indicating that ABA signaling varies with the organ. Understanding the ABA responses in an organ-specific manner is crucial to fully understand hormone action and plant responses to osmotic stress. Moreover, this study provides new insights into how ABA regulates plant responses and acclimation to water deficits.
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