Physiological and Molecular Responses of Six Apple Rootstocks to Osmotic Stress

Abstract

The growth and productivity of several apple rootstocks have been evaluated in various previous studies. However, limited information is available on their tolerance to osmotic stress. In the present study, the physiological and molecular responses as well as abscisic acid (ABA) levels were assessed in six apple rootstocks (M26, V3, G41, G935, B9 and B118) osmotically stressed with polyethylene glycol (PEG, 30%) application under greenhouse conditions. Our results showed that V3, G41, G935 and B9 had higher relative water content (RWC), and lower electrolyte leakage (EL) under stress conditions compared to M26 and B118. Additionally, water use efficiency (WUE) was higher in V3, G41 and B9 than M26, which might be partially due to the lower transpiration rate in these tolerant rootstocks. V3, G41 and B9 rootstocks also displayed high endogenous ABA levels which was combined with a reduction in stomatal conductance and decreased water loss. At the transcriptional level, genes involved in ABA-dependent and ABA-independent pathways, e.g., SnRK, DREB, ERD and MYC2, showed higher expression in V3, G41, G935 and B9 rootstocks compared to M26 in response to stress. In contrast, WRKY29 was down-regulated in response to stress in the tolerant rootstocks, and its expression was negatively correlated with ABA content and stomatal closure. Overall, the findings of this study showed that B9, V3 and G41 displayed better osmotic stress tolerance followed by G935 then M26 and B118 rootstocks.

A genome-wide association study of lateral root number for Asian cotton (Gossypium arboreum L.)

“…A recent study found that OsWRKY29 could act as a new ABA signaling repressor for seed dormancy in rice with RNAi mutant lines displaying greater sensitivity after ABA treatment (Zhou et al 2020). The WRKY29 gene was negatively correlated with the ABA content, and down-regulated in the tolerant rootstocks under osmotic stress (Hezema et al 2021). RBOHA is a burst oxidase homolog protein, which participates in diverse biological processes in higher plants (Arthikala and Quinto 2018).…”

A Multi-Level Approach as a Powerful Tool to Identify and Characterize Some Italian Autochthonous Common Bean (Phaseolus vulgaris L.) Landraces under a Changing Environment

“…The RWC is an important indicator of water status in plants because it reflects the balance between water supply to the tissues and transpiration rate [ 67 ]. Reductions in RWC under salt and osmotic stress, caused by low osmotic potential, are commonly reported in the literature [ 68 , 69 ]. In detail, it has been argued that salt-tolerant plants decrease the hydraulic conductance of their roots, thereby reducing the delivery of (salty) water to the shoot and resulting in reduced water potential in their leaves [ 70 ].…”

Molecular Traits for Adaptation to Drought and Salt Stress in Birch, Oak and Poplar Species

“…In turn, up-regulation of WRKY29 in the BpHOX2 transgenic B. platyphylla may lead to an increase in susceptibility to PEG-mediated osmotic stress. Hezema et al [102] demonstrated that in apple rootstocks under hard osmotic stress WRKY29 acts as a negative regulator of ABA-mediated stomatal closure, which can lead to water leakage. Thus, the WRKY29 gene is down-regulated under osmotic stress in apple rootstocks.…”

“…Thus, the drought and the PEG-mediated osmotic stress in B. platyphylla induced the expression of many genes of the ROS scavenging enzymes and their TFs, activation of water deprivation and mechanical damage responses, and cell wall protection. In addition, it can be assumed that there is a system for the formation of an adequate stress response, which implies a balance between tolerance and susceptibility by controlling of ABA-mediated stomatal movement [97,102].…”