Increasing salinity is a worldwide problem, but the knowledge on how salt enters
the roots of plants remains largely unknown. Non-selective cation channels
(NSCCs) have been suggested to be the major pathway for the entry of sodium
ions (Na+) in several species. The hypothesis tested in this research is that PQ
loop (PQL) proteins could form NSCCs, mediate some of the Na+ influx into the
root and contribute to ion accumulation and the inhibition of growth in saline
conditions. This is based on previous preliminary evidence indicating similarities in
the properties of NSCC currents and currents mediated by PQL proteins, such as
the inhibition of an inward cation current mediated by PQL proteins by high external
calcium and pH acidification. PQL family members belonging to clade one in
Arabidopsis and barley were characterized using a reverse genetics approach,
electrophysiology and high-throughput phenotyping. Expression of AtPQL1a and
HvPQL1 in HEK293 cells increased Na+ and K+ inward currents in whole cell
membranes. However, when GFP-tagged PQL proteins were transiently
overexpressed in tobacco leaf cells, the proteins appeared to localize to
intracellular membrane structures. Based on q-RT-PCR, the levels of mRNA of
AtPQL1a, AtPQL1b and AtPQL1c is higher in salt stressed plants compared to
control plants in the shoot tissue, while the mRNA levels in the root tissue did not
change in response to stress. Salt stress responses of lines with altered
expression of AtPQL1a, AtPQL1b and AtPQL1c were examined using RGB and
chlorophyll fluorescence imaging of plants growing in soil in a controlled
environment chamber. Decreases in the levels of expression of AtPQL1a,
AtPQL1b and AtPQL1c resulted in larger rosettes, when measured seven days
after salt stress imposition. Interestingly, overexpression of AtPQL1a also resulted
in plants having larger rosettes in salt stress conditions. Differences between the
mutants and the wild-type plants were not observed at earlier stages, suggesting
that PQLs might be involved in long-term responses to salt stress. These results
contribute towards a better understanding of the role of PQLs in salinity tolerance
and provide new targets for crop improvement.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/660184 |
| Date | 10 1900 |
| Creators | Alqahtani, Mashael Daghash Saeed |
| Contributors | Tester, Mark A., Biological and Environmental Sciences and Engineering (BESE) Division, Blilou, Ikram, Pain, Arnab, Pardo, José, Pain, Arnab, Pardo, José |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2020-11-24, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2020-11-24. |
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