Hua Wei, Xiling Wang, Yuqing He, Hang Xu, Lei Wang

EMBO Journal; 2021 Feb 1; 40(3):e105086.  doi: 10.15252/embj.2020105086. 

Abstract

The roles of clock components in salt stress tolerance remain incompletely characterized in rice. Here, we show that, among OsPRR (Oryza sativa Pseudo-Response Regulator) family members, OsPRR73 specifically confers salt tolerance in rice. Notably, the grain size and yield of osprr73 null mutants were significantly decreased in the presence of salt stress, with accumulated higher level of reactive oxygen species and sodium ions. RNA sequencing and biochemical assays identified OsHKT2;1, encoding a plasma membrane-localized Na⁺ transporter, as a transcriptional target of OsPRR73 in mediating salt tolerance. Correspondingly, null mutants of OsHKT2;1 displayed an increased tolerance to salt stress. Immunoprecipitation-mass spectrometry (IP-MS) assays further identified HDAC10 as nuclear interactor of OsPRR73 and co-repressor of OsHKT2;1. Consistently, H3K9ac histone marks at OsHKT2;1 promoter regions were significantly reduced in osprr73 mutant. Together, our findings reveal that salt-induced OsPRR73 expression confers salt tolerance by recruiting HDAC10 to transcriptionally repress OsHKT2;1, thus reducing cellular Na⁺ accumulation. This exemplifies a new molecular link between clock components and salt stress tolerance in rice.

See: https://pubmed.ncbi.nlm.nih.gov/33347628/

Figure 1: OsPRR73 positively regulates salinity tolerance in rice.

A.Schematic diagram showing the T-DNA insertion sites in rice osprr73^T-DNA mutant (hereafter named as osprr73).

B.OsPRR73 confers salinity stress tolerance in rice. The seedlings of Dongjin (DJ, the wild-type control), osprr73, and the complementation line of osprr73 (abbreviated as Com-L1) grown under 12-h light/12-h dark conditions for 28 days (left panel), transferred to 180 mM NaCl for 21 days (middle panel) and recovered for 12 and 24 days (the two right panels), respectively. Scale bar, 5 cm.

C.Statistical analysis of the survival rate of DJ, osprr73, and Com-L1 plants in (B) after recovery 12 days. Data are presented as mean ± SD. (n from 4 biological replicates, and 24 plants were tested in each of biological replicates). (***) P ≤ 0.001 were generated by Student’s t-test.

D.Diagram showing the target and mutated sites of OsPPR73 by CRISPR/Cas9-based genome editing. The PR and CCT are the abbreviations of Pseudo-Response and COSTANS, COSTANS-LIKE, and TOC1 domains, respectively. The target sequences within the first exon of OsPRR73 were shown with the green boxes. PAM sequences were labeled with underline within the green boxes.

E.Null mutant of osprr73 in Nipponbare (NIP) background by genome editing displayed hypersensitivity to NaCl treatment. Scale bar, 5 cm.

F.Survival rate of NIP (wild type of CRISPR lines) and osprr73-C (C stands for CRISPR) plants in (E) after recovery 9 days. Data are presented as mean ± SD. n = 4 biological replicates, 24 plants for each biological replicate. (*) P ≤ 0.05 and (***) P ≤ 0.001 were generated by Student’s t-test.

G, H.Quantification of chlorophyll content and electrolyte leakage of WT and osprr73 mutants with or without 180 mM NaCl treatment for 7 days. Data are presented as mean ± SD. n = 3, biological replicates, and asterisks represent significant difference among means by Student’s t-test with (*) P ≤ 0.05, (**) P ≤ 0.01, (***) P ≤ 0.001.