Snijders, R. | bioRxiv Science

bioRxiv2023

Woolly mutation with Get02 locus overcomes the polygenic nature of trichome-based pest resistance in tomato

Type-IV glandular trichomes, which only occur in the juvenile phase of tomato development, produce acylsugars (AS) that broadly protect against arthropod herbivory. Previously, we introgressed the capacity to retain type-IV trichomes in the adult phase from Solanum galapagense into the cv. Micro-Tom (MT). The resulting MT-Get line contained five loci associated with enhancing the density of type-IV trichomes in adult plants. We genetically dissected MT-Get and obtained a sub-line containing only the locus on chromosome 2 (MT- Get02). This genotype displayed about half the density of type-IV trichomes compared to the wild progenitor. However, when we stacked the gain-of-function allele of WOOLLY, which codes for a HD-ZIP IV transcription factor, MT-Get02/Wo exhibited double the number of type-IV trichomes compared to S. galapagense. This discovery corroborates previous reports positioning WOOLLY as a master regulator of trichome development. AS levels in MT-Get02/Wo were comparable to the wild progenitor, although the composition of AS types differed, especially regarding less AS with medium-length acyl chains. Agronomical parameters of MT-Get02/Wo, including yield, were comparable to MT. Pest resistance assays showed enhanced protection against whitefly, caterpillar, and the fungus Septoria lycopersici. However, resistance levels did not reach that of the wild progenitor, suggesting the specificity of particulars AS types in the pest resistance mechanism. Our findings in trichome-mediated resistance advance the development of robust, naturally resistant tomato varieties, harnessing the potential of natural genetic variation. Moreover, by manipulating only two loci, we achieved exceptional results for a highly complex, polygenic trait, such as herbivory resistance in tomato.

plant biology↗

bioRxiv2021

Medicago SPX1 and SPX3 regulate phosphate homeostasis, mycorrhizal colonization and arbuscule degradation

To acquire sufficient mineral nutrients such as phosphate (Pi) from the soil, most plants engage in a symbiosis with arbuscular mycorrhizal (AM) fungi. Attracted by plant-secreted strigolactones, the fungi colonize the roots and form highly-branched hyphal structures called arbuscules inside inner cortex cells. It is essential that the host plant controls the different steps of this interaction to maintain its symbiotic nature. However, how plants sense the amount of Pi obtained from the fungus and how this determines the arbuscule lifetime is far from understood. Here, we show that Medicago truncatula SPX-domain containing proteins SPX1 and SPX3 regulate root phosphate starvation responses as well as fungal colonization and arbuscule degradation. SPX1 and SPX3 are induced upon phosphate starvation but become restricted to arbuscule-containing cells upon establishment of the symbiosis. Under Pi-limiting conditions they facilitate the expression of the strigolactone biosynthesis gene DWARF27, which correlates with increased fungal branching by root exudates and increased root colonization. Later, in the arbuscule-containing cells SPX1 and SPX3 redundantly control the timely degradation of arbuscules. This regulation does not seem to involve direct interactions with known transcriptional regulators of arbuscule degradation. We propose a model where SPX1 and SPX3 control arbuscule degeneration in a Pi-dependent manner via a yet-to-identify negative regulator.

plant biology↗