Molecular aspects of dormancy in peach (Prunus persica [L.] Batsch.)

Abstract

En estos cuatros años en los que he estado trabajando, he conocido a mucha gente que me ha ayudado en distintas formas para la realización de esta tesis y por eso he pensado en agradecerlos.En primer lugar quería dar las gracias a mis directores por la dedicación que me han prestado. A Gerardo y Marisa por darme la oportunidad de trabajar en el IVIA y de desarrollar esta tesis. A Gabino por haber estado ahí en todo momento, para enseñar y contestar a mis preguntas, sin su apoyo no habría podido llegar hasta aquí. ABSTRACTDormancy is one of the most important adaptive mechanisms developed by perennial plants, in order to survive the low temperatures of autumn and winter in temperate climates. The study of the genes regulated during dormancy release is crucial to understand the process, with the final objective of the development of new varieties with a better adaptation to certain environments; and this is particularly important considering the increasing economical weight of fruit crops in low and medium chilling regions as the Mediterranean area. We focused on the molecular and physiological mechanisms underlying the maintenance and release of seasonal dormancy in peach. In order to achieve this we first used suppression subtractive hybridization (SSH) to identify genes expressed in dormant and dormancy-released buds in two cultivars with different chilling requirements, 'Zincal-5' and 'Springlady', and subsequently validated their differential expression utilizing a peach cDNA microarray platform containing transcripts enriched in flower buds. Additionally, we carried out a genome-wide search of peach genes related to dormancy release by hybridizing the previous cDNA microarray with mRNA samples from 10 cultivars showing different dormancy behaviour, followed by an expression correlation analysis.Among the most relevant genes identified in these two first works, we found the DORMANCY ASSOCIATED MADS-box genes DAM4, DAM5 and DAM6, described independently by other groups working in peach and other species. The central role of DAM genes in dormancy regulation has also been confirmed by additional functional approaches as the analysis of the non-dormant evg mutant, QTL analysis, and transgenic approaches.In our second work we focused on the molecular mechanisms of DAM6 down-regulation concomitant with dormancy release in flower buds. A ChIP analysis of DAM6 promoter and structural gene revealed chromatin modification events similar to those observed in vernalization of Arabidopsis and cereals. We showed that DAM6 is transcriptionally active in dormant buds collected in October, when a short chromatin region around its ATG was trimethylated in histone H3 at K4 (H3K4) and acetylated at the N-terminal tail of H3. Concomitantly with DAM6 repression, H3K4 became demethylated and H3 deacetylated. Later H3K27 was found trimethylated along a genomic region larger than 4kb, including promoter, coding sequence and intron. Due to their relevance in dormancy regulation, DAM genes could be used as expression markers to assess...

Distinctive Gene Expression Patterns Define Endodormancy to Ecodormancy Transition in Apricot and Peach

“…One set of major dormancy regulators known in fruit trees are DAMs, with previous studies reporting that increased trimethylation of H3K27 and decreased H3K4 trimethylation represses the expression of DAMs during dormancy (Leida, 2012;Leida et al, 2012b;Saito et al, 2015a). In our study, all six copies of DAM genes decreased at the transition from endodormancy to ecodormancy, and were maintained at a low level after ecodormancy (Figure 1 and Supplementary Figure 8).…”

“…Prunus flowers are sensitive to frost damage, and maintenance of winter dormancy for a sufficient time period is essential to prevent frost damage to delicate reproductive tissues, especially during the spring months when temperatures may fluctuate. This is one of the most important adaptation mechanisms that ensure perennial plants survive low winter temperatures and coordinates the timing of reproductive activities (Campoy et al, 2011;Leida, 2012). There have been many efforts to find the possible regulation factors of winter dormancy in perennial trees, including examinations of internal factors such as phase change, circadian clock, and hormones, and external factors including photoperiod, temperature, light radiation, and water (Perry, 1971;Rohde and Bhalerao, 2007;Allona et al, 2008;Cooke et al, 2012;Maurya and Bhalerao, 2017).…”

Evaluation of dormancy break in some selected peach (Prunus persica) cultivars

“…In winter, buds are already dormant so they are usually not damaged by frosts. This means that dormancy is one of the most important adaptation mechanisms that enable the survival of perennial plants in winter periods of low temperatures (Taylor 2008;Leida 2012). The process of dormancy thus determines how the woody fruit species can survive during the winter season and early spring without any damage to shoots and, above all, flower buds (Allona et al 2008).…”