Biology subjects

Redzich, L.

Publications and source records attributed to Redzich, L..

3 recordsLinked to original sources

bioRxiv2026

TALE-independent transcriptional activation of the rice executor gene Xa23 is regulated via histone acetylation during zygote development

Transcription activator-like effectors (TALEs) from Xanthomonas activate transcription of executor (E) genes in host plants, leading to cell death and thereby restricting proliferation of biotrophic pathogens. Because E gene transcripts had only been detected upon activation by cognate Xanthomonas TALEs, E genes were thought to function exclusively in plant immunity. Here, we detect TALE-independent transcription of the rice E gene Xa23 in zygotes 4-6 hours after gamete fusion. Histone deacetylase inhibition induces Xa23 transcription in unfertilized egg cells, implicating histone acetylation in Xa23 regulation. We identified potential cis-regulatory elements and transcription start sites associated with native Xa23 transcription during zygote development. Together, our findings suggest that Xa23 is a developmentally regulated gene with a native role during early zygote development. This supports a previously proposed model in which E genes have native functions in development, while fortuitous upstream polymorphisms can create TALE-binding sites that convert them into immune executors.

plant biology↗

bioRxiv2025

Differentiation of Xanthomonas oryzae pv. oryzae in vitro and during rice leaf infection

Highlights- Xoo produces filamentous morphology, which is transient and yields pleomorphic progenies in vitro - In planta, initial attachment of rod-shaped Xoo is detected at xylem pits - The Xoo infection front migrates basipetally in the vascular bundle and progresses laterally from major to minor veins via transverse veins - Xoo breaks out of the xylem vessels and enter the neighboring xylem parenchyma - Xoo assumes filamentous morphology that can traverse from the xylem across the bundle sheath into mesophyll tissue - Mobility in xylem vessels depends predominantly on rod-shaped Xoo, while infection of mesophyll tissue at later stages appears to be linked to filamentous morphology SummaryXanthomonas oryzae pv. oryzae (Xoo) is classified as a xylem pathogen responsible for bacterial blight of rice causing substantial yield losses in Asia and Africa. Xoo virulence depends on the ability to trigger SWEET sucrose efflux transporters in the xylem parenchyma (XP) by injection of transcription activation like effectors (TALe) into host cells, likely to access host-derived sucrose. To establish infection, Xoo must overcome physical barriers, immune responses and the hydraulic xylem flow. To gain insights into the colonization process, we used translational SWEET11a-GUS reporter lines, scanning electron microscopy, and confocal laser scanning microscopy of Xoo tagged with a fluorescent protein. We found that Xoo can differentiate in vitro into filamentous forms. We mapped the infection route of Xoo along the vasculature, identified distinct spatiotemporal phases of Xoo colonization marked by rod-shaped and, notably, filamentous Xoo cells. Rod-shaped Xoo were found to attach to xylem pits during basipetal progression of the infection. Notably, we found that at later infection stages, Xoo could enter the XP. Strikingly, Xoo adopted a filamentous phenotype that traversed bundle sheath cells and entered mesophyll cells. Chlorosis and necrosis of leaves is thus likely not just due to blockage of xylem flow, but to direct tissue damage. Filamentation had been reported as important for virulence of human pathogens e.g. Yersinia pestis, uropathogenic E. coli and Shigella and had been associated to sugar utilization in Bacillus subtilis. We thus hypothesize that Xoo differentiation during host colonization is critical for virulence. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/680524v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@f66d8borg.highwire.dtl.DTLVardef@91ca66org.highwire.dtl.DTLVardef@17f2846org.highwire.dtl.DTLVardef@12d46e7_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

Restricted transmission of Xanthomonas oryzae pv. oryzae from rice roots to shoots detected by a rapid root infection system

Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight in rice, is primarily studied in the context of foliar infections. However, infected stubble and irrigation water may serve as reservoirs and be responsible for seedling stage root infections in the field, especially during transplanting. Here, we established a coleoptile crown root-based infection protocol to investigate whether gene-for-gene interactions between Xoo TAL effectors and SWEET sucrose uniporter susceptibility genes occur in the root xylem, and whether the disease can propagate from roots to seedling shoots. Using translational SWEET11a-GUS reporter lines under control of the native SWEET11a promoter, we observed progressive infection as indicated by accumulation of SWEET11a-GUS fusion protein in infected coleoptile crown roots. However, we did not detect progression of GUS accumulation beyond the coleoptile node, nor did we detect blight symptoms on the young leaves. Notably, the xylem, at least during early stages of infection remained functional as shown by Rhodamine B tracer, consistent with transfer of xylem constituents via living cells at the coleoptile node that did not allow bacteria to pass. Furthermore, the root infection protocol is a [~]4x faster compared to standard leaf-clipping assays (roots assay: 11 days from sowing, compared to 39 days for clip infection), enabling more rapid assessment of TAL effector repertoire and plant defense responses with translational SWEET-GUS reporter lines. Our findings expand our understanding of Xoo infection routes and provide a valuable tool for resistance testing and pathogen surveillance.

plant biology↗