Biology subjects

Desikan, P.

Publications and source records attributed to Desikan, P..

3 recordsLinked to original sources

bioRxiv2026

Antagonistic action of a nuclear hormone receptor pair coordinates a switch from lytic to biotrophic effector production in a plant-parasitic nematode

Pathogens secrete overlapping and sequential waves of effectors to manipulate their host, and yet the regulators that conduct the ensemble are poorly understood. Here, we identify the Dorsal Gland Regulator DGR-1 in the beet cyst nematode Heterodera schachtii. DGR-1 controls the expression of 131 putative effectors, acting as a dual-functional switch that "switches off" early stage effectors involved in plant invasion, and "switches on" later stage effectors associated with biotrophic establishment in the host. Interestingly, DGR-1 works antagonistically with the only other known transcriptional regulator of effectors in plant-parasitic nematodes, the Subventral Gland Regulator-1 (SUGR-1), to coordinate this apparent switch from lytic to biotrophic effector production. Together, DGR-1 and SUGR-1 control the expression of nearly one half of all H. schachtii early-stage effectors, and over one fifth of effectors of any kind. The requirement to activate lytic effector functions in the cortex, and biotrophic effector functions in the vascular cylinder, suggests that this transcription factor pair must differentially respond to signals from the host. Consistent with this, we find that diffusates from the roots of A. thaliana Casparian strip mutant myb36/sgn3, which are enriched in molecules ordinarily restricted to the vascular cylinder, upregulate dgr-1, but not sugr-1, compared to Col-0. Taken together, these data indicate that H. schachtii responds to compartmentalised host-derived signals to appropriately regulate spatiotemporal effector expression during infection. Given that misregulating DGR-1 results in delayed development of parasitic nematodes in Arabidopsis and Mustard, strategies which impair effector regulation as a whole may hold promise for crop protection against these agriculturally important pathogens.

pathology↗

bioRxiv2026

Better late than never: the impact of hatching time on Heterodera schachtii parasitism

Plant-parasitic nematodes are a diverse, polyphyletic group of plant pathogens which can infect most plant tissues and all major crops. Amongst the most damaging clades are the cyst nematodes, which can remain dormant in the soil for decades as infection-competent, developmentally arrested, second-stage juveniles in eggs. Hatching is stimulated by a variety of factors. However, the impact of hatching factor responsiveness on nematode morphology, physiology, gene expression, and infection biology has not been explored. We examined the impact of hatching time on the beet cyst nematode, Heterodera schachtii. We found that late hatchers invaded host roots and established feeding sites in greater numbers than early hatchers. We demonstrate variation in baseline parasitism gene expression and in responsiveness of genes to effectostimulins, small, plant-derived molecules which upregulate parasitism genes. Three quarters of effectostimulin-induced transcriptional changes were also modulated, either positively or negatively, by hatching time. While there were no observable morphological differences between early and late hatching nematodes on the day of their emergence from the egg, the late hatchers displayed signs of faster utilisation of internal energy reserves after 7 days at 4{degrees}C, as evidenced by less body area attributed to fat, than early hatchers. Finally, we found no evidence of substantive genetic differences between early and late hatchers, they were representative of a single population, despite the observed differences in infection, gene expression, and physiology. Taken together, non-genetic differences likely drive late hatchers to more rapidly utilise their internal energy reserves, to be more responsive to host-derived signals, and to be ultimately more infective than their early hatching counterparts.

molecular biology↗

bioRxiv2025

The host range paradox of Meloidogyne incognita: a physiological and transcriptomic analysis of nine susceptible interactions across six plant orders

The plant-parasitic nematode Meloidogyne incognita is the pathogen with the broadest host range among all known biotrophic interactions. This species is also the single most damaging of a group of agriculturally important plant-parasites, which together are estimated to contribute to losses in excess of $170 billion/year to world agriculture. Understanding how M. incognita is able to infect representatives from most orders of flowering plants, covering more than 3000 species, addresses a fundamentally important question of how pathogens adapt to their host-environment, and may inform control of a pathogen which threatens global food security. Here, we analyse the plant-nematode infection phenotype, and cross-kingdom transcriptome, of nine interactions across six orders of flowering plants at 25 days post infection. At this stage, majority of nematodes found within roots were immature and mature females (49.2% - 91.8%). Our data show that the phylogenetic distribution of hosts does not explain the phenotypic distribution of parasitism. Interestingly, though, M. incognita do have distinct transcriptional responses to different groups of hosts, but in a pattern which is independent of host phylogenetic. Three distinct nematode "transcriptional programmes" - Group 1, 2, and 3 - are evident, and we find that effectors are neither uniformly deployed across hosts, nor across groups of hosts. Importantly, we show that this differential deployment of effectors can have profound consequences for host specificity. Finally, we show that there is essentially no widespread core gall transcriptome at 25 days post infection, prompting the proposal of a model best described as "all roads lead to Rome".

plant biology↗