Abstract
We have identified a gene (PpSAP1) of Prunus persica coding for a stress-associated protein (SAP) containing Zn-finger domains A20 and AN1. SAPs have been described as regulators of the abiotic stress response in plant species, emerging as potential candidates for improvement of stress tolerance in plants. PpSAP1 was highly expressed in leaves and dormant buds, being down-regulated before bud dormancy release. PpSAP1 expression was moderately induced by water stresses and heat in buds. In addition, it was found that PpSAP1 strongly interacts with polyubiquitin proteins in the yeast two-hybrid system. The overexpression of PpSAP1 in transgenic plum plants led to alterations in leaf shape and an increase of water retention under drought stress. Moreover, we established that leaf morphological alterations were concomitant with a reduced cell size and down-regulation of genes involved in cell growth, such as GROWTH-REGULATING FACTOR (GRF)1-like, TONOPLAST INTRINSIC PROTEIN (TIP)-like, and TARGET OF RAPAMYCIN (TOR)-like. Especially, the inverse expression pattern of PpSAP1 and TOR-like in transgenic plum and peach buds suggests a role of PpSAP1 in cell expansion through the regulation of TOR pathway.
Highlights
Perennial plants in temperate climates have to cope with seasonal fluctuations in temperature
In previous transcriptomic studies in our group we have identified a Zn-finger protein gene expressed in dormant flower buds of peach, which is down-regulated concomitantly with developmental processes leading to bud dormancy release[4, 5]
Ppa012373m expression reached its lowest level in January and February samples, previous to bud dormancy release date which was experimentally estimated between February and March sampling dates
Summary
Perennial plants in temperate climates have to cope with seasonal fluctuations in temperature. Gene expression down-regulation occurs concomitantly with dormancy release in genotypes with different chilling requirements, and gene expression regulation seems to associate with the developmental stage of buds under apparently variable environmental circumstances[4]. This Zn-finger protein belongs to a family of plant regulators known as stress-associated proteins (SAP), with known homologs in animals[6, 7]. The related OsSAP1 and OsSAP11 from rice interact with the receptor-like kinase OsRLCK253, which in turn confers tolerance to salt and water deficit stress in transgenic Arabidopsis plants[19]. A conformational change in response to redox conditions has been observed in AtSAP12 from Arabidopsis, which could behave as a sensor and transmitter of redox imbalances triggered by different stresses[21]
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