Abstract
Dormancy is an adaptive mechanism that allows temperate deciduous plants to survive unfavorable winter conditions. In the present work, we investigated the possible function of abscisic acid (ABA) on the endodormancy process in pear. The ABA content increased during pear flower bud endodormancy establishment and decreased towards endodormancy release. In total, 39 putative genes related to ABA metabolism and signal transductions were identified from pear genome. During the para- to endodormancy transition, PpNCED-2 and PpNCED-3 had high expression levels, while PpCYP707As expression levels were low. However, during endodormancy, the expression of PpCYP707A-3 sharply increased with increasing cold accumulation. At the same time, the ABA content of pear buds declined, and the percentage of bud breaks rapidly increased. On the other hand, the expression levels of PpPYLs, PpPP2Cs, PpSnRK2s, and PpABI4/ABI5s were also changed during the pear flower bud dormancy cycle. Furthermore, exogenous ABA application to para-dormant buds significantly reduced the bud breaks and accelerated the transition to endodormancy. During the whole treatment time, the expression level of PpPP2C-12 decreased to a greater extent in ABA-treated buds than in control. However, the expression levels of PpSnRK2-1, PpSnRK2-4, and PpABI5-1 were higher in ABA-treated buds. Our results indicated that PpCYP707A-3 and PpNCEDs play pivotal roles on the regulation of endodormancy release, while ABA signal transduction pathway also appears to be involved in the process. The present work provided the basic information about the function of ABA-related genes during pear flower bud dormancy process.
Highlights
Bud dormancy is an adaptive mechanism of temperate deciduous fruit trees that allows them to survive detrimental winter environments [1]
In this work we provided the information supporting the hypothesis that abscisic acid (ABA) is a positive regulator of endodormancy induction and a negative regulator of endodormancy release
PpABI4 and PpABI5-2 expression levels significantly increased from para- to endodormancy in pear flower buds (Figures 3 and 5c), while the PpABI5-1 gene did not significantly change
Summary
Bud dormancy is an adaptive mechanism of temperate deciduous fruit trees that allows them to survive detrimental winter environments [1]. In grape, the ABA content in buds was consistent with the NCED expression pattern, peaking during endodormancy, and gradually decreasing during the transition to ecodormancy [11]. PpCYP707A had a high expression level during the transition from endo- to ecodormancy in the Japanese pear “Kosui” [13] These results were similar with those of peach, in which PpeCYP707A3 was highly expressed during the endodormancy release, leading to a lower ABA content [12]. The expression levels of PpPP2C-3/5/8/9/13, which negatively regulate ABA-signaling pathway, increased in parallel with decreases in the ABA content (Figure 5a) These results suggest that these genes may take part in dormancy regulation. PpABI4 and PpABI5-2 expression levels significantly increased from para- to endodormancy in pear flower buds (Figures 3 and 5c), while the PpABI5-1 gene did not significantly change. We cannot exclude the involvement of other genes in the regulation of endodormancy process, as most of these genes subjected to the regulation in posttranslational level, their detailed functions need to be further studied
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