Salt-stress-induced ABA accumulation is more sensitively triggered in roots than in shoots

Abstract

Salt-stress-induced ABA accumulation in maize root tissues was compared with that in leaf tissues. While salt stress with NaCl resulted in a significant ABA accumulation in root tissues (up to 10-fold), the same stress only led to a small ABA accumulation in leaf tissues (about 1-fold). Pretreatment with ethylene glycol (EG), a permeable and inert monomer of PEG, could prevent the shrinkage of cell volume and completely block the ABA accumulation in leaf tissues under salt stress, but substantial salt-induced ABA accumulation was still observed in root tissues following such pretreatment. Hypotonic salt solutions, i.e. below 100 mM NaCl, still induced a significant ABA accumulation (more than 3-fold) in roots, but showed no effect on that in leaf tissues. Results suggest that the salt-stress-induced ABA accumulation in roots may also be triggered by an osmosensing mechanism, which is in addition to the perception of the changes in reduced cellular volume or plasmalemma tension that leads to ABA accumulation in leaves. When leaf and root tissues were immersed into salt solutions, salt entered into the cells as a function of time and salt concentrations. Such entrance apparently led to a loss of sensitivity of leaf tissues to accumulate ABA under the salt stress, and also prevented the leaf tissues from responding to further air-drying in terms of ABA accumulation. Roots showed no such responses. Results suggest that the entrance of salt into leaf cells brought about some toxic effect that might have reduced the capability of leaf cells to produce ABA under dehydration.

A novel in vitro tissue culture approach to study salt stress responses in citrus

“…When shoots were cultured 503 in vitro, no accumulations of ABA were observed in any of 504 the studied genotypes, which seem to discard an ABA 505 dependent signaling. These results are similar to those 506 obtained in maize by Jia et al (2002), who observed that 507 NaCl treatment only induced a small ABA accumulation in 508 leaf tissues, whereas on the contrary, the same treatment of 509 NaCl caused a significant ABA accumulation in root 510 tissues.…”

“…These 498 results suggested the existence of an osmosensing mecha-499 nism and also the organ-specific nature of such a response. 500 This suggestion is also supported by the fact that gene 501 expression in response to salt stress usually is organ-or 502 tissue-specific (Jia et al 2002). When shoots were cultured 503 in vitro, no accumulations of ABA were observed in any of 504 the studied genotypes, which seem to discard an ABA 505 dependent signaling.…”

Abscisic Acid- and Stress-Induced Highly Proline-Rich Glycoproteins Regulate Root Growth in Rice

“…Root growth is significantly affected by environmental stimuli. Salinity and water stress induce ABA accumulation in roots (Zhang and Davies, 1987;Jia et al, 2002). The involvement of ABA in root development under water deficit conditions has also been examined (Sharp and LeNoble, 2002;Sharp et al, 2004).…”

Regulation of Gene Expression in Response to Abiotic Stress in Plants

“…The SOS3 activates SOS2, a protein kinase to be/thr. Salinity induces the biosynthesis and accumulation of the stress hormone in plants, the ABA (Jia et al 2002) and also induces accumulation of ROS (Hernandez et al, 2001). The ROS-mediated signaling under salt stress, occurs through the mitogen-activated protein kinases (MAPKs) (Pei et al 2000).…”