Defining the Cell Wall, Cell Cycle and Chromatin Landmarks in the Responses of Brachypodium distachyon to Salinity

Abstract

Excess salinity is a major stress that limits crop yields. Here, we used the model grass Brachypodium distachyon (Brachypodium) reference line Bd21 in order to define the key molecular events in the responses to salt during germination. Salt was applied either throughout the germination period (“salt stress”) or only after root emergence (“salt shock”). Germination was affected at ≥100 mM and root elongation at ≥75 mM NaCl. The expression of arabinogalactan proteins (AGPs), FLA1, FLA10, FLA11, AGP20 and AGP26, which regulate cell wall expansion (especially FLA11), were mostly induced by the “salt stress” but to a lesser extent by “salt shock”. Cytological assessment using two AGP epitopes, JIM8 and JIM13 indicated that “salt stress” increases the fluorescence signals in rhizodermal and exodermal cell wall. Cell division was suppressed at >75 mM NaCl. The cell cycle genes (CDKB1, CDKB2, CYCA3, CYCB1, WEE1) were induced by “salt stress” in a concentration-dependent manner but not CDKA, CYCA and CYCLIN-D4-1-RELATED. Under “salt shock”, the cell cycle genes were optimally expressed at 100 mM NaCl. These changes were consistent with the cell cycle arrest, possibly at the G1 phase. The salt-induced genomic damage was linked with the oxidative events via an increased glutathione accumulation. Histone acetylation and methylation and DNA methylation were visualized by immunofluorescence. Histone H4 acetylation at lysine 5 increased strongly whereas DNA methylation decreased with the application of salt. Taken together, we suggest that salt-induced oxidative stress causes genomic damage but that it also has epigenetic effects, which might modulate the cell cycle and AGP expression gene. Based on these landmarks, we aim to encourage functional genomics studies on the responses of Brachypodium to salt.

Exogenous Myo-Inositol Alleviates Salt Stress by Enhancing Antioxidants and Membrane Stability via the Upregulation of Stress Responsive Genes in Chenopodium quinoa L.

“…The present study revealed the beneficial influence of an exogenously applied metabolite, MYO, in quinoa under salinity stress. Salinity stress reduces the growth of cells, cell proliferation by declining cell cycle genes [2,52], mitotic index, and relative cell division rate [53]. Salinity stress reduces growth by inducing osmotic and ionic stress, resulting in hampered cellular functioning, thereby restricting plant growth [3].…”

Plant CDKs—Driving the Cell Cycle through Climate Change

“…The pause in cell cycle progression under salt stress is one of the survival mechanisms in Brachypodium grasses where there was an accumulation of CYCB1;1 , CDKB1 , and CDKB2 and a reduction in CYCD4;1 level at salt concentrations of 100 and 200 mM of NaCl, which suggests a blockage of the cell cycle in the G1 phase ( Figure 2 C). This hypothesis is supported by the induction of WEE1 , which is one of the CDKA inhibitors [ 169 ] ( Figure 2 C). Other genes involved in cell cycle regulation have already been shown to have their expression levels altered in response to environmental stresses, such as drought.…”

Enhancers as potential targets for engineering salinity stress tolerance in crop plants

“…Recently, a significant effect of salinity stress on chromatin accessibility has been demonstrated in Arabidopsis (Raxwal et al 2020). Salinity stress has been found to influence H4K5ac histone mark positively and DNA methylation negatively in Brachypodium (Wolny et al 2021). The histone marks known to be associated with enhancers, H3K4me3 and H3K27me3, were found to vary in response to salinity stress in castor bean and soybean (Han et al 2020;Sun et al 2019aSun et al , 2019b.…”