Regulation of α-expansins genes in Arabidopsis thaliana seeds during post-osmopriming germination
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Seed osmopriming is a pre-sowing treatment that involves limitation of the seed water imbibition, so that pre-germinative metabolic activities proceed without radicular protrusion. This technique is used for improving germination rate, uniformity of seedling growth and hastening the time to start germination. In Arabidopsis thaliana, seed germination has been associated with the induction of enzymes involved in cell wall modifications, such as expansins. The α-expansins (EXPAs) are involved in cell wall relaxation and extension during seed germination. We used online tools to identify AtEXPA genes with preferential expression during seed germination and RT-qPCR to study the expression of five EXPA genes at different germination stages of non-primed and osmoprimed seeds. In silico promoter analysis of these genes showed that motifs similar to cis-acting elements related to abiotic stress, light and phytohormone responses are the most overrepresented in promoters of these AtEXPA genes, showing that their expression is likely be regulated by intrinsic developmental and environmental signals during Arabidopsis seed germination. The osmopriming conditioning had a decreased time and mean to 50% germination without affecting the percentage of final seed germination. The dried PEG-treated seeds showed noticeable high mRNA levels earlier at the beginning of water imbibition (18 h), showing that transcripts of all five EXPA isoforms were significantly produced during the osmopriming process. The strong up-regulation of these AtEXPA genes, mainly AtEXPA2, were associated with the earlier germination of the osmoprimed seeds, which qualifies them to monitor osmopriming procedures and the advancement of germination.
KeywordsArabidopsis thaliana α-Expansins Osmopriming Seed germination
We are grateful by the suggestions provided by Dr. Peter E. Toorop. All authors read and approved the final manuscript.
LGEV and AFR conceived and designed the experiments. FLA, CCC and NBMN performed the germination and priming experiments. AFR and NVS carried out the bioinformatics analysis. AFR and TBS carried out the RT-qPCR assays and analyzed the data. LGEV, AFR and NVC wrote the manuscript.
Compliance with ethical standards
Conflict of interest
NVS has received a grant from São Paulo Research Foundation (FAPESP) and Coordination for the Improvement of Higher Education Personnel (CAPES) for the fellowship during her doctor degree and National Council for Scientific and Technological Development—CNPq for the fellowship during her master degree. TBS has received a grant from Coordination for the Improvement of Higher Education Personnel (CAPES) for postdoctoral fellowship. LGEV has received a grant from National Council for Scientific and Technological Development—CNPq for the research fellowship. AFR, FLA, CCC, NBM declare that they have no conflict of interest.
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