No abstract

Gene transcription is counterbalanced by mRNA decay processes that regulate transcript quality and quantity. We show here that the evolutionarily conserved DHH1/DDX6-like RNA HELICASEs of Arabidopsis thaliana control the ephemerality of a subset of cellular mRNAs.These RNA helicases co-localize with key markers of processing bodies and stress granules and contribute to their subcellular dynamics. These RHs function to limit the precocious accumulation and translation of stress-responsive mRNAs associated with autoimmunity and growth inhibition under non-stress conditions. Given the conservation of this RH subfamily, they may control basal levels of conditionally-regulated mRNAs in diverse eukaryotes, accelerating responses without penalty. XRN1/4 . These 5' and 3' pathways have substrate specificity, but are not mutually exclusive.When decapping-dependent decay is compromised in Arabidopsis, the 3'-to-5' exoribonuclease SOV can compensate to control mRNA abundance and homeostasis 10,11 . Spatiotemporal regulation of mRNA decay is critical for the cellular transcriptome adjustment in response to both developmental and environmental cues in plants 1 . Dysfunction in decapping due to loss-of-function of non-redundant components results in post-embryonic lethality (DCP1, DCP2, VCS, and DCP5) or severe growth alterations (LSM1 and PAT1) [12][13][14][15][16] .The cause of the developmental defects in some decapping mutants is associated with disruption of mRNA quality control and small interfering (si)RNA production 17 . However, there is limited knowledge of the role of the decay machinery in the spatial and temporal turnover of specific mRNAs and the connections between turnover and mRNA translation and mobilization to PBs and SGs. Mutations in the mRNA decay machinery have been identified in genetic screens for altered sensitivity to biotic and abiotic stresses 16,[18][19][20][21][22][23][24] , yet there is poor understanding of the importance of mRNA decay in restricting accumulation of mRNAs that provide stress resilience but constrain growth.The DHH1/DDX6 family of DEAD-box RNA helicases is conserved across eukaryotes 25 .These proteins function at the nexus between mRNA translation, storage and decay, mediating translational repression and initiating mRNA degradation [26][27][28][29][30][31][32][33] . For example, yeast DHH1 can activate mRNA decapping 34 , promote translational repression 35 , and associate with ribosomes to sense the codon-dependent rate of translational elongation to trigger cotranslational decay 36 . However, the transcript-specific role of these helicases is generally understudied. Here we identify the Arabidopsis DHH1/DDX6-like proteins RNA HELICASE 6 (RH6), RH8, and RH12 as additive and functionally redundant mRNA decay factors required for growth and development.Severe deficiency of RH6, RH8 and RH12 function impairs PB and SG formation, and shifts the transcriptome and translatome homeostasis so that defense-and other stress-responsive mRNAs accumulate despite when grown under standar...

Phosphorus (P) availability and soil water are two important environmental factors in lowland rice paddies. They limit the ability of rice to form mutualistic associations with arbuscular mycorrhizal fungi (AMF). The dynamics of this symbiotic interaction are intensified by phosphorus deficiency and attenuated by anaerobic conditions. However, the effects of combined phosphorus deficiency and anaerobic conditions on AMF symbiosis in paddy soil were unproven. The main objective of this study is to determine the influence of phosphorus and water availabilities on indigenous AMF colonization and community in Sangyod Muang Phatthalung (SMP) rice. Rice seedlings were grown in pots containing P-deficient organic paddy soil with or without phosphorus fertilization under non-flooded and flooded conditions for 2, 4 and 6 weeks. The application and omission of P soil fertilization influenced phosphate accumulations in rice seedlings, producing conditions of P-sufficiency and P-deficiency, respectively, in the plants. To determine the effects of phosphorus and water availabilities on AMF colonization and community structures, roots were analyzed microscopically and molecularly. Flooding considerably reduced the intensity of indigenous AMF root colonization whereas the nonenrichment of P availability did not. Reduced AMF colonization was concomitant with lower abundances of two major Glomeromycota ASVs in roots under flooding. This result suggested that soil water availability plays the primary role in shaping AMF communities in SMP roots. This study emphasized the primacy of water management when considering the use of AMF in the production of SMP rice in an organic cultivation system.

Genetic diversity is important for developing salt‐tolerant rice (Oryza sativa L.) cultivars. Certain Thai rice accessions display salt tolerance at the adult or reproductive stage, but their response to salinity at the seedling stage is unknown. In this study, a total of 10 rice cultivars/line, including eight Thai cultivars and standard salt‐tolerant cultivar and susceptible line, were screened using a hydroponic system to identify salt‐tolerant genotypes at the seedling stage. Different morphophysiological indicators were used to classify tolerant and susceptible genotypes. Phylogenetic analyses were performed to determine the evolutionary relationships between the cultivars. Results showed that ‘Lai Mahk’, ‘Jao Khao’, ‘Luang Pratahn’, and ‘Ma Gawk’ exhibited salt stress tolerance comparable with the standard salt‐tolerance check ‘Pokkali’. Whole‐exome single‐nucleotide polymorphism (SNP)‐based phylogenetic analysis showed that the Thai rice cultivars were monophyletic and distantly related to Pokkali and IR29. Lai Mahk and Luang Pratahn were found closely related when using the whole‐exome SNPs for the analysis. This is also the case for the analysis of SNPs from 164 salt‐tolerance genes and transcription regulatory genes. The tolerant cultivars shared the same haplotype for 16 genes. Overall, the findings of this study identified four salt‐stress‐tolerant Thai rice cultivars, which could be used in rice breeding programs for salinity tolerance.