Biology subjects

Sagi, M.

Publications and source records attributed to Sagi, M..

5 recordsLinked to original sources

bioRxiv2023

AAO2 impairment improves aldehyde detoxification by AAO3 in Arabidopsis leaves exposed to UVC or Rose Bengal.

Among the three active aldehyde oxidases in Arabidopsis thaliana leaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably, aao2KO mutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and HNE than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of the absence of AAO2 expression on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response of aao1Single mutant, aao2KO mutants and single mutants of aao3Ss. Notably, aao3Ss exhibited similar aldehyde accumulation and chlorophyll content to aao2KO treated with UV-C or Rose-Bengal. In contrast, wild-type and aao1S exhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KO leaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity in aao2KO mutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity in aao2KO and aao3Ss leaves compared to wild-type treated with UV-C or Rose Bengal. The similar abscisic acid level accumulated in leaves of unstressed or stressed genotypes indicates that aldehyde detoxification by AAO3 is the cause for better stress resistance in aao2KO mutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type, aao2KO, and molybdenum-cofactor sulfurase (aba3-1) mutant plants revealed that the active AAO2 in WT employs sulfuration processes essential for AAO3 activity level, resulting in the lower AAO3 activity in WT than AAO3 activity in aao2KO.

plant biology↗

bioRxiv2021

Ureides are similarly accumulated in response to UV-C irradiation and wound but differently remobilized during recovery in Arabidopsis leaves.

To examine a role of purine degraded metabolites in response to wounding or UV-C stress, the Arabidopsis wild-type and Atxdh1 KO mutants, defective in xanthine dehydrogenase1 (XDH1), were exposed to wounding and UV-C irradiation stress. In Atxdh1 mutant, wounding or UV-C stresses resulted in lower fresh-weight, increased senescence symptoms and higher tissue cell death rate compared to Wild-type. Additionally, Wild-type exhibited lower levels of oxidative stress indicators; reactive oxygen species and malondialdehyde than Atxdh1 mutant leaves. Notably, purine degradation transcripts and proteins were orchestrated to lead to enhanced ureide levels in Wild-type leaves 24 h after applying UV-C or wound stress. Yet, different remobilization of the accumulated ureides was noticed 72 h after stresses application. In plants treated with UV-C the allantoin level was highest in young leaves, whereas in wounded plants it was lowest in the young leaves, accumulated mainly in the middle and wounded leaves. The results indicate that in UV-C treated Wild-type, during the recovery period from stress, ureides are remobilized from the lower older leaves to support young leaf growth. In contrast, after wounding, the ureides are remobilized to the young leaves, yet more to the middle wounded leaves, to function as antioxidants and/or healing agents. HighlightUV-C and wound triggers purine degradation in old and damaged leaves to increase ureides accumulation in stress dependent rate. Impairment in purine degradation results in premature senescence in leaves.

plant biology↗

bioRxiv2020

Impairment in O-acetylserine-(thiol) lyase A and B, but not C, confers higher selenate sensitivity and uncovers role for A, B and C as L-Cys and L-SeCys desulfhydrases in Arabidopsis

The role of the cytosolic O-acetylserine-(thiol) lyase A (OASTLA), chloroplastic OASTLB and mitochondrion OASTLC in plant resistance/sensitivity to selenate was studied in Arabidopsis plants. Impairment in OASTLA and B resulted in reduced biomass, chlorophyll and soluble protein levels compared with impaired OASTL C and Wild-Type treated with selenate. The lower organic-Se and protein-Se levels followed by decreased organic-S, S in proteins and total glutathione in oastlA and oastlB compared to Wild-Type and oastlC are indicative that Se accumulation is not the main cause for the stress symptoms, but rather the interference of Se with the S-reduction pathway. The increase in sulfite oxidase, adenosine 5'-phosphosulfate reductase, sulfite reductase and OASTL activity levels, followed by enhanced sulfite and sulfide, indicate a futile anabolic S-starvation response to selenate-induced organic-S catabolism in oastlA and oastlB compared to Wild-Type and oastlC. Additionally, the catabolic pathway of L-cysteine degradation was enhanced by selenate, and similar to L-cysteine producing activity, oastlA and B exhibited a significant decrease in L-cysteine desulfhydrase (DES) activity, compared with WT, indicating a major role of OASTLs in L-cysteine degradation. This notion was further evidenced by sulfide dependent DES in-gel activity, immunoblotting, immunoprecipitation with specific antibodies and identification of unique peptides in activity bands generated by OASTLA, B and C. Similar responses of the OASTLs in Seleno-Cysteine degradation was demonstrated in selenate stressed plants. Notably, no L-cysteine and L-Seleno-Cysteine DES activity bands but those related to OASTLs were evident. These results indicate the significance of OASTLs in degrading L-cysteine and L-SelenoCysteine in Arabidopsis. SummaryThe cytosolic OASTLA and chloroplastic OASTLB have significantly higher desulfhydrase activity rates than the cytosolic DES1 and are able to degrade L-Cys and L-SeCys to sulfide and selenide, respectively in Arabidopsis.

biochemistry↗

bioRxiv2020

Spectrum of genes for inherited hearing loss in the Israeli Jewish population, including the novel human deafness gene ATOH1

Mutations in more than 150 genes are responsible for inherited hearing loss, with thousands of different, severe causal alleles that vary among populations. The Israeli Jewish population includes communities of diverse geographic origins, revealing a wide range of deafness-associated variants and enabling clinical characterization of the associated phenotypes. Our goal was to identify the genetic causes of inherited hearing loss in this population, and to determine relationships among genotype, phenotype, and ethnicity. Genomic DNA samples from informative relatives of 88 multiplex families, all of self-identified Jewish ancestry, with either non-syndromic or syndromic hearing loss, were sequenced for known and candidate deafness genes using the HEar-Seq gene panel. The genetic causes of hearing loss were identified for 60% of the families. One gene was encountered for the first time in human hearing loss: ATOH1 (Atonal), a basic helix-loop-helix transcription factor responsible for autosomal dominant progressive hearing loss in a five-generation family. Our results demonstrate that genomic sequencing with a gene panel dedicated to hearing loss is effective for genetic diagnoses in a diverse population. Comprehensive sequencing enables well-informed genetic counseling and clinical management by medical geneticists, otolaryngologists, audiologists, and speech therapists and can be integrated into newborn screening for deafness.

genetics↗

bioRxiv2017

Pre-mature senescence in the oldest leaves of low nitrate-grown Atxdh1 mutant uncovers a role for purine catabolism in plant nitrogen metabolism

The nitrogen rich ureides allantoin and allantoate, are known to play a role in nitrogen delivery in Leguminosae, in addition to their role as reactive oxygen species scavengers. However, their role as a nitrogen source in non-legume plants has not been shown. Xanthine dehydrogenase1 (AtXDH1) activity is a catalytic bottleneck step in purine catabolism. Atxdh1 mutant exhibited early leaf senescence, lower soluble protein and organic-N levels as compared to wild-type (WT) older leaves when grown with 1 mM nitrate, whereas under 5mM, mutant plants were comparable to WT. Similar nitrate-dependent senescence phenotypes were evident in the older leaves of allantoinase (Ataln) and allantoate amidohydrolase (Ataah) mutants, impaired in further downstream steps of purine catabolism. Importantly, under low nitrate conditions, xanthine was accumulated in older leaves of Atxdh1, whereas allantoin in both older and younger leaves of Ataln but not in WT leaves, indicating remobilization of xanthine degraded products from older to younger leaves. Supporting this notion, ureide transporters UPS1, UPS2 and UPS5 were enhanced in older leaves of 1 mM nitrate-fed WT as compared to 5 mM. Enhanced AtXDH, AtAAH and purine catabolic transcripts, were detected in WT grown in low nitrate, indicating regulation at protein and transcript levels. Higher nitrate reductase activity in Atxdh1 than WT leaves, indicates their need for nitrate assimilation products. It is further demonstrated that the absence of remobilized purine-degraded N from older leaves is the cause for senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of nitrate starved Atxdh1 plants.\n\nSummaryThe absence of remobilized purine-degraded N from older to the young growing leaves is the cause for senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of nitrate starved Atxdh1 plants.

biochemistry↗