SET DOMAIN GROUP 721 protein functions in saline–alkaline stress tolerance in the model rice variety Kitaake

Abstract

To isolate the genetic locus responsible for saline-alkaline stress tolerance, we developed a high-throughput activation tagging-based T-DNA insertion mutagenesis method using the model rice (Oryza sativa L.) variety Kitaake. One of the activation-tagged insertion lines, activation tagging 7 (AC7), showed increased tolerance to saline-alkaline stress. This phenotype resulted from the overexpression of a gene that encodes a SET DOMAIN GROUP 721 protein with H3K4 methyltransferase activity. Transgenic plants overexpressing OsSDG721 showed saline-alkaline stress-tolerant phenotypes, along with increased leaf angle, advanced heading and ripening dates. By contrast, ossdg721 loss-of-function mutants showed increased sensitivity to saline-alkaline stress characterized by decreased survival rates and reduction in plant height, grain size, grain weight and leaf angle. RNA sequencing (RNAseq) analysis of wild-type Kitaake and ossdg721 mutants indicated that OsSDG721 positively regulates the expression level of HIGH-AFFINITY POTASSIUM (K + ) TRANSPORTER1;5 (OsHKT1;5), which encodes a Na + -selective transporter that maintains K + /Na + homeostasis under salt stress. Furthermore, we showed that OsSDG721 binds to and deposits the H3K4me3 mark in the promoter and coding region of OsHKT1;5, thereby upregulating OsHKT1;5 expression under saline-alkaline stress. Overall, by generating Kitaake activationtagging pools, we established that the H3K4 methyltransferase OsSDG721 enhances salinealkaline stress tolerance in rice.

Dynamic regulation of DNA methylation and histone modifications in response to abiotic stresses in plants

“…The H3K27me3 mark is highly enriched in the gene body of Arabidopsis HKT1 , and the activation of HKT1 expression under salinity stress is caused by the removal of H3K27me3 (Sani et al, 2013). Under saline‐alkaline stress, SDG721, a SET DOMAIN GROUP rice protein with H3K4 methyltransferase activity, binds to and deposits the H3K4 mark in the promoter and coding region of HKT1;5 to regulate its expression level (Liu et al, 2021b). In cotton ( Gossypium hirsutum ), genes encoding the JmjC domain‐containing proteins were induced by salt stress treatment.…”

The coordinated regulation mechanism of rice plant architecture and its tolerance to stress

“…In addition to leaf morphology, plant height, spike shape, tiller, and root development are important morphological factors in regulating rice plant architecture and stress response. OsSDG721 encodes a TRITHORAX-like protein that affects plant height and spike shape, and positively regulates salt tolerance in rice by regulating the methylation of OsHKT1;5 ( Jiang et al., 2018 ; Liu et al., 2021 ). OsDRO1 is involved in the morphological development of rice roots.…”

Plasma membrane‐localized Hsp40/DNAJ chaperone protein facilitates OsSUVH7‐OsBAG4‐OsMYB106 transcriptional complex formation for OsHKT1;5 activation

“…japonica cv. Kitaake) background (Liu et al, 2021) to isolate mutants not only show salt stress related phenotypes but also display altered OsHKT1;5 expression levels in roots. In the T2 generation, line 22 showed reduced survival rates under salt stress (100 mM NaCl) (Figure 1A, B), with reduced OsHKT1;5 expression in roots (Figure 1C).…”

“…A whole genome-scale activation tagging pool was used in this study (Liu et al, 2021). All genotypes were in kitaake (a japonica cultivar) background.…”