In:
Science, American Association for the Advancement of Science (AAAS), Vol. 379, No. 6638 ( 2023-03-24)
Abstract:
According to the Food and Agriculture Organization (FAO), there are currently 〉 1 billion ha of land affected by salt. Among these, ~60% are classified as sodic soil areas. These have high pH and are dominated by sodium bicarbonate (NaHCO 3 ) and sodium carbonate (Na 2 CO 3 ). The effects of global warming and a lack of fresh water will lead to 〉 50% of arable land becoming affected by salt by 2050, thus severely affecting the world’s food security. Identifying and/or engineering sodic-tolerant crops is imperative to solve this challenge. Although salinity tolerance has been studied extensively, alkalinity tolerance in plants has not been studied in depth. RATIONALE Sorghum originates from Africa, where it can grow in harsh environments. As a result, sorghum has evolved greater tolerance to adapt to multiple abiotic stresses compared with other crops. Some sorghum varieties can survive in sodic soil with a pH as high as 10.0. A genome-wide association study (GWAS) analysis was performed with a large sorghum association panel consisting of 352 representative sorghum accessions. We detected a major locus, Alkaline tolerance 1 ( AT1 ), linked to alkaline tolerance. We found that AT1 , encoding an atypical G protein γ subunit (a homolog to rice GS3 ), contributes to alkaline sensitivity by modulating the efflux of hydrogen peroxide (H 2 O 2 ) under environmental stress. RESULTS On the basis of the results of the GWAS analysis, we sequenced the cDNA regions of SbAT1 ( Sorghum bicolor AT1 ) in 37 sorghum accessions with different degrees of alkaline sensitivity. Two typical haplotypes (Hap1 and Hap2) of SbAT1 were identified according to the five leading variant sites associated with sorghum alkali sensitivity. Hap1 encodes an intact SbAT1. A frame shift mutation (from “G” to “GGTGGC”) within Hap2 results in a premature stop codon probably encoding a truncated protein with only 136 amino acids at the N terminus (named Sbat1 ). To confirm the function of the AT1 locus, we generated a pair of near-isogenic lines (NILs) with two AT1 haplotypes to assess the allelic effect of AT1 on sorghum tolerance to alkali. We found that the Sbat1 allele (Hap2), encoding a truncated form of SbAT1, increased plant alkaline sensitivity compared with wild-type full-length SbAT1 (Hap1). Overexpression of AT1/GS3 reduced alkaline tolerance in sorghum and rice, and overexpression of the C-terminal truncated AT1/GS3 showed a more severe alkaline sensitive response. This was confirmed in millet and rice, which suggests that AT1/GS3 functions negatively in plant alkali tolerance. By contrast, knockout (ko) of AT1/GS3 increased tolerance to alkaline stress in sorghum, millet, rice, and maize, which indicates a conserved pathway in monocot crops. By immunoprecipitation in combination with mass spectrometry (IP-MS), we found that AT1/GS3 interacts with aquaporin PIP2s that are involved in reactive oxygen species (ROS) homeostasis. Genetic analysis showed that OsPIP2;1 ko /2;2 ko had lower alkaline tolerance than their wild-type control. The redox probe Cyto-roGFP2-Orp1 sensing H 2 O 2 in the cytoplasm was applied. The results showed that, upon alkaline treatment, the relative H 2 O 2 level increased in OsPIP2;1 ko /2;2 ko compared with wild-type plants. These results suggested that the phosphorylation of aquaporins could modulate the efflux of H 2 O 2 . Gγ negatively regulates the phosphorylation of PIP2;1, leading to elevated ROS levels in plants under alkaline stress. To assess the application of the AT1/GS3 gene for crop production, field tests were carried out. We found that the nonfunctional mutant, either obtained from natural varieties or generated by gene editing in several monocots, including sorghum, millet, rice, and maize, can improve the field performance of crops in terms of biomass or grain production when cultivated on sodic lands. CONCLUSION We concluded that SbAT1 encodes an atypical G protein γ subunit and inhibits the phosphorylation of aquaporins that may be used as H 2 O 2 exporters under alkaline stress. With this knowledge, genetically engineered crops with knockouts of AT1 homologs or use of natural nonfunctional alleles could greatly improve crop yield in sodic lands. This may contribute to maximizing the use of global sodic lands to ensure food security. Genetic modification of AT1 enhances alkaline stress tolerance. The Gγ subunit, AT1, pairs with Gβ to negatively modulate the phosphorylation level of PIP2 aquaporins. Thus, AT1 reduces the H 2 O 2 export activity of PIP2s, leading to the overaccumulation of H 2 O 2 and resulting in alkaline stress sensitivity. By contrast, the artificial or natural knockouts of AT1 homologs release the inhibition of PIP2s by AT1 in crops and have improved survival rates and yield under alkaline stress. [Figure created using BioRender]
Type of Medium:
Online Resource
ISSN:
0036-8075
,
1095-9203
DOI:
10.1126/science.ade8416
Language:
English
Publisher:
American Association for the Advancement of Science (AAAS)
Publication Date:
2023
detail.hit.zdb_id:
128410-1
detail.hit.zdb_id:
2066996-3
SSG:
11
Permalink
