Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2023.05.18.541275

Regulation of metal homeostasis by two F-group bZIP transcription factors bZIP48 and bZIP50 in rice

Tao, Q.·Ci, X. T.·Yun, Z. Q.·Ping, L. H.·Xiang, L. J.
View original source ↗Export metadata ↓

Abstract

Zinc (Zn) is an essential microelement for plants as well as for human beings, and it regulates numerous metabolic process and protein activity. Zn deficiency not only impairs plant growth and development, but also affects human health. Rice (Oryza sativa L.) is a staple food for more than half of the worlds population, but how Zn homeostasis in rice is maintained is largely unknown. Here, we demonstrate that two F-group bZIP transcription factors, OsbZIP48 and OsbZIP50, are important for metal homeostasis in rice. Mutation of OsbZIP48 and OsbZIP50 impairs plant growth and reduces Zn, Fe, and Cu content in shoots. The N-terminus of either OsbZIP48 or OsbZIP50 contains two cysteine- and histidine-rich (CHR) domains, deletion or mutation of these CHR domains increases nucleus localization of OsbZIP48 and OsbZIP50. Both OsbZIP48 and OsbZIP50 have transcriptional activation activity, and the expression of 1117 genes involved in metal uptake, phenylpropanoid biosynthetic process, cell wall organization, et al., is reduced in OsbZIP48 and OsbZIP50 double mutant than that in wild-type ZH11 plant under Zn deficiency. Both OsbZIP48 and OsbZIP50 bind to the promoter region of the ZIP family transporter gene OsZIP10 in rice, and activate the promoter activity of ZDRE cis-element derived from the OsZIP10 promoter in effector-reporter assays. Mutation of the CHR domain of OsbZIP48 in OsbZIP50 mutant background increases the content of Zn/Fe/Cu in brown rice seeds and leaves. Thus, this study reveals that OsbZIP48 and OsbZIP50 regulate metal homeostasis, especially under Zn deficiency in rice, and provides candidate target genes for biofortification of micronutrients in future. significance statementZinc (Zn) is an essential microelement not only for plants but also for human beings. This paper shows that the N-terminal cysteine- and histidine-rich domain of OsbZIP48/50 is important for their nucleus localization, therefore transcriptional activity, and reveals the downstream genes of OsbZIP48/50 involved in metal homeostasis under Zn deficiency in rice.

Explore related subjects

plant biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Tao, Q., Ci, X. T., Yun, Z. Q., Ping, L. H., Xiang, L. J.. 2023-05-21. Regulation of metal homeostasis by two F-group bZIP transcription factors bZIP48 and bZIP50 in rice. https://doi.org/10.1101/2023.05.18.541275

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Loss of starch synthase IIa alleviates the negative impact of high temperature on rice starch during grain filling

High temperatures during grain filling stage are becoming increasingly frequent, compromising both grain and eating quality and thereby driving demand for heat-resilient cultivars. Such conditions are known to reduce the expression of granule-bound starch synthase I (GBSSI) and starch branching enzyme IIb (BEIIb), which are involved in starch biosynthesis, resulting in a decrease in amylose content and an increase in long-chain amylopectin. Thus, the present study introduced functional mutation in starch synthase IIa (SSIIa) that increases the proportion of short amylopectin chains to genetically compensate for the high-temperature-induced increase in amylopectin long chain. Rice lines carrying the ss2a mutation were grown at two locations with cooler (Akita) and warmer (Okayama) temperatures. Their grain traits, starch structure, and eating quality were compared. The ss2a mutant lines showed an increased proportion of short amylopectin chains as well as an increased apparent amylose content. Furthermore, these alterations in starch structure varied with the grain-filling temperature of the cultivation sites, ultimately affected eating quality. These results suggest that enriching short amylopectin chain via the ss2a mutation can counteract the increase in long amylopectin chain caused by high temperatures during grain filling, thereby maintaining a desirable starch structure and eating quality.

plant biology↗
bioRxiv2026

Analysis of SpCas9 on- and off-target effects in high efficiency multiplex editing in Arabidopsis

RNA-guided nucleases (RGNs), such as Cas9 from Streptococcus pyogenes (SpCas9), are widely used for plant genome editing. Previous surveys for off-targeting, the modification of unintended targets with similarity to the intended target, indicate high specificity of SpCas9 in plant cells. However, off-targeting has not been assessed for efficiency-optimized editing systems combined with extensive multiplexing, which might increase the likelihood of cleavage at unintended sites. We therefore analyzed Arabidopsis thaliana lines that had been extensively mutagenized using zCas9i and up to 29 gRNAs addressing >45 target sites over several rounds of editing. Genomes were sequenced by short- and long-read technologies, and genome-wide variants were catalogued. Our pipeline for variant calling reliably detected RGN-induced mutations at on-targets. When excluding these on-target modifications, variants were detected in edited lines at frequencies similar to those previously reported for spontaneous mutations. In further analyses, we did not find any evidence for an origin of these variants from RGN activity. Our data are thus consistent with high specificity of SpCas9. In contrast, we detected genomic reorganization events upon editing at two complex loci, RPP1 and RPP7, encompassing multiple homologous genes, and also identified an allele by WGS that had escaped detection by amplicon sequencing. We conclude that, while off-targets may efficiently be avoided by selection of specific gRNAs, on-target modifications may be more extensive than intended, especially at complex loci and/or during multiplexing.

plant biology↗
bioRxiv2026

A cellulose synthase interactome uncovers BAG proteins as regulators of cellulose synthase homeostasis

Cellulose synthase complexes build the load-bearing cellulose microfibrils of plant cell walls, yet how the abundance of their catalytic CELLULOSE SYNTHASE A (CESA) subunits is maintained remains unclear. Here, we used multi-bait TurboID proximity labelling with ten cellulose-synthesis-associated baits and six subcellular controls to define a high-confidence cellulose synthase neighbourhood. Stringent spatial and recurrence-based filtering yielded a core network of 119 interactions among 44 proteins and identified three members of the conserved Bcl-2-associated athanogene (BAG) family as previously unrecognised regulators of cellulose synthase homeostasis. BAG1-3 associated with primary-wall CESAs in reciprocal proximity-labelling experiments. Arabidopsis bag mutants showed reduced cellulose accumulation, hypersensitivity to cellulose-synthesis inhibitors, and markedly decreased CESA protein abundance without corresponding changes in CESA transcript levels. Loss of BAG function also increased the accumulation of CESA6 in vacuolar compartments. These findings identify BAG proteins as previously unrecognised regulators of cellulose synthase homeostasis and link a conserved proteostasis-associated protein family to plant cell wall biosynthesis. More broadly, the study establishes multi-bait proximity labelling, combined with cell location-specific controls, as a strategy for resolving dynamic protein networks whose components traffic through multiple subcellular compartments.

plant biology↗