PHO2 suppresses arbuscular mycorrhizal symbiosis in high phosphate conditions
Authors: Birch, S., Perryman, S., Ellison, E., Foreman, N., Mekjan, N., Williams, A., Bate-Weldon, M., Ralfs, T., Pucker, B., Whiting, M., Hope, M. S., Wallington, E., Field, K., Choi, J.
The study identifies the rice E2 ubiquitin‑conjugating enzyme PHO2 as a key negative regulator of arbuscular mycorrhizal (AM) colonisation under high phosphate conditions. pho2 mutants in Oryza sativa (and Nicotiana benthamiana) maintain AM fungal entry and exhibit enhanced direct and symbiotic phosphate accumulation, linked to sustained expression of AM‑related genes despite phosphate sufficiency.
The study demonstrates that calcium-dependent protein kinases NbCDPK4 and NbCDPK5 directly phosphorylate the NADPH oxidase NbRBOHB at Ser‑123, enhancing sustained ROS production during effector-triggered immunity in Nicotiana benthamiana. Constitutively active CDPKs also upregulate NbRBOHB transcription, and phosphorylation of Ser‑123 is amplified by Ca2+ influx triggered by an autoactive helper NLR (NRC4). These results define a NbCDPK‑NbRBOHB signaling module that links NLR activation to prolonged ROS bursts in ETI.
The improved auxin signalling via entire mutation enhances aluminium tolerance in tomato
Authors: Silva, R., Siqueira, J. A., Batista-Silva, W., Ferreira-Silva, M., Thiago, W., Vargas, J. R., Vilela, G., Robson, R., Neto, D. F. M., Azevedo, A. A., Ribeiro, C., Fernie, A., Nunes-Nesi, A., Araujo, W.
The study investigates how auxin signaling influences aluminium tolerance using tomato mutants with altered auxin sensitivity, showing that the auxin‑hypersensitive entire mutant tolerates Al stress while the auxin‑reduced dgt mutant is more sensitive. Differences in reactive oxygen species accumulation and root transition‑zone cell differentiation correlate with distinct metabolic responses, suggesting that modifying auxin perception can enhance crop Al tolerance.
Drought drives reversible disengagement of root-mycorrhizal symbiosis
Authors: Akmakjian, G. Z., Nozue, K., Nakayama, H., Borowsky, A. T., Morris, A. M., Baker, K., Canto-Pastor, A., Paszkowski, U., Sinha, N., Brady, S., Bailey-Serres, J.
The study shows that during drought, rice (Oryza sativa) downregulates nutrient acquisition and arbuscular mycorrhizal (AM) symbiosis genes, causing the fungal partner to enter metabolic quiescence and retract hyphae, but upon re-watering the symbiosis is rapidly reactivated. This reversible dynamic suggests that plant‑fungus mutualisms are fragile under fluctuating water availability.
The study employed computational approaches to characterize the SUMOylation (ULP) machinery in Asian rice (Oryza sativa), analyzing phylogenetic relationships, transcriptional patterns, and protein structures across the reference genome, a population panel, and wild relatives. Findings reveal an expansion of ULP genes in cultivated rice, suggesting selection pressure during breeding and implicating specific ULPs in biotic and abiotic stress responses, providing resources for rice improvement.
The study evaluated barley stripe mosaic virus (BSMV) and foxtail mosaic virus (FoMV) vectors for virus-induced gene silencing (VIGS) and virus-mediated overexpression (VOX) in several Oryza sativa cultivars, finding that neither vector altered gene expression despite successful assays in wheat and extensive optimization. The lack of photobleaching with BSMV-PDS and absent GFP fluorescence with FoMV suggest intrinsic resistance mechanisms in rice, highlighting species-specific limitations of virus-enabled reverse genetics and the need for alternative vectors.
The study measured flower opening time and flower exposure duration (FED) in rice cultivars and performed controlled crossing experiments under short‑day and long‑day conditions, finding that when FED overlap exceeds ~20 min, cross‑pollination frequency often exceeds 60 % and can reach 100 %. These results overturn the long‑standing view that rice cross‑pollination is <2 % and highlight the need to investigate genetic factors underlying F1 sterility.
A copper-dependent, redox-based hydrogen peroxide perception in plants
Authors: Ishihama, N., Fukuda, Y., Shirano, Y., Takizawa, K., Hiroyama, R., Fujimoto, K. J., Ito, H., Nishimura, M., Yanai, T., Inoue, T., Shirasu, K., Laohavisit, A.
The study resolves the ectodomain structure of the plant-specific LRR‑RLK CARD1 (HPCA1) and reveals a surface‑exposed copper ion coordinated by histidines that is essential for hydrogen peroxide signaling. Combined structural, genetic, and biochemical analyses show that previously identified cysteine residues are not required for signal perception, establishing CARD1 as the first copper‑dependent redox receptor.
The study investigated how native soil microbes affect heat tolerance in soybean (Glycine max) by comparing plants grown in natural versus microbiome‑disturbed soils under optimal and elevated temperatures. Using 16S rRNA and ITS sequencing alongside non‑targeted root metabolomics, the authors found significant shifts in bacterial and fungal communities, suppressed nodule‑forming bacteria, and altered root metabolites that correlated with reduced nodulation efficiency under heat stress. Integrated multi‑omics analyses linked microbial composition to metabolite profiles and nitrogen‑fixation traits, highlighting a coordinated response of the root physiological system to combined heat and microbiome perturbations.
The study evaluated the genetically encoded redox biosensor roGFP2-Orp1 for monitoring extracellular redox dynamics in diverse land plants, revealing that re‑oxidation rates in the apoplast differ between Physcomitrium patens and Arabidopsis thaliana and are accelerated by immune activation. Comparisons across tip‑growing cells showed no intracellular redox gradient but a partially reduced extracellular sensor in Nicotiana tabacum pollen tubes, indicating species‑ and cell‑type‑specific oxidative processes.