Dual regulation of water retention and cell growth by a stress-associated protein (SAP) gene in Prunus

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.

Tomato SlSAP3, a member of the stress‐associated protein family, is a positive regulator of immunity against Pseudomonas syringae pv. tomato DC3000

“…It is therefore likely that ubiquitin E3 ligase activity may not be a common feature for the A20/AN1 domain‐containing SAPs. On the other hand, the Arabidopsis AtSAP5 and AtSAP9, Prunus PpSAP1 and orchid Pha13 were found to interact with polyubiquitinated proteins or with UPS shuttling factors such as RADs (Chang et al ., ; Choi et al ., ; Farmer et al ., ; Kang et al ., ; Lloret et al ., ). The A20 domains in AtSAP5 and Pha13 are responsible for ubiquitin binding activity (Chang et al ., ; Choi et al ., ).…”

“…However, the mechanism by which the interaction of SlSAP3‐SlBOBs regulates immunity is an open question to be investigated further. Because both SAP and BOB proteins seem to be associated with UPS via interaction with UPS subunits or components (Choi et al ., ; Farmer et al ., ; Fu et al ., ; Gunsalus et al ., ; Kang et al ., ; Lloret et al ., ; Saeki, ), the interaction of SlSAP3‐SlBOBs in planta might initiate an event that results in the degradation of one or both of them and of other unknown targeting proteins upon pathogen infection. Further characterization of SlSAP3 and SlBOB targets of SlSAP3 will be helpful to understand the biochemical mechanism of SlSAP3‐SlBOBs complex in tomato immunity.…”

“…Besides, some SAPs were found to interact with UPS components, such as ubiquitin receptors RAD23s, which are capable of targeting ubiquitylated substrates to UPS (Farmer et al ., ; Fu et al ., ; Saeki, ). For instance, Arabidopsis AtSAP5, Prunus PpSAP1 and orchid Pha13 were found to interact with polyubiquitinated proteins (Chang et al ., ; Choi et al ., ; Lloret et al ., ). AtSAP9 was found to interact with RAD23b and RAD23d, which act as shuttling factors of ubiquitin conjugates (Farmer et al ., ; Guzder et al ., ; Kang et al ., ).…”

Modulation of Dormancy and Growth Responses in Reproductive Buds of Temperate Trees

“…The study of gene expression in flower buds also has served to identify a stress associated protein ( SAP )-like gene ( PpSAP1 ) expressed in dormant buds and down-regulated concomitantly with dormancy release ( Lloret et al, 2017a ). SAP-like proteins containing Zn-finger domains A20 and AN1 have been found to regulate the abiotic stress response in different especies ( Giri et al, 2013 ), most likely by an ubiquitin-related mechanism.…”

Drought and heat stress-related proteins: an update about their functional relevance in imparting stress tolerance in agricultural crops

“…Upregulation of the A. littoralis, AlSAP gene in rice, also enhanced grain yield by 50-90% under drought stress in the field (Ghneim-Herrera et al 2017). The expression of Prunus persica, PpSAP1, was induced by heat and water stress and increased water retention ability in transgenic plums (Lloret et al 2017). Similarly, in Arabidopsis, overexpression of AtSAP13 transcripts improved tolerance to drought along with other stresses (Dixit et al 2017).…”