Loss of function mutation of the Rapid Alkalinization Factor (RALF1)-like peptide in the dandelion Taraxacum koksaghyz entails a high-biomass taproot phenotype

Abstract

The Russian dandelion ( Taraxacum koksaghyz ) is a promising source of inulin and natural rubber because large amounts of both feedstocks can be extracted from its roots. However, the domestication of T . koksaghyz requires the development of stable agronomic traits such as higher yields of inulin and natural rubber, a higher root biomass, and an agronomically preferable root morphology which is more suitable for cultivation and harvesting. Arabidopsis thaliana Rapid Alkalinisation Factor 1 (RALF1) has been shown to suppress root growth. We identified the T . koksaghyz orthologue TkRALF-like 1 and knocked out the corresponding gene ( TkRALFL1 ) using the CRISPR/Cas9 system to determine its impact on root morphology, biomass, and inulin and natural rubber yields. The TkRALFL1 knockout lines more frequently developed a taproot phenotype which is easier to cultivate and harvest, as well as a higher root biomass and greater yields of both inulin and natural rubber. The TkRALFL1 gene could therefore be suitable as a genetic marker to support the breeding of profitable new dandelion varieties with improved agronomic traits. To our knowledge, this is the first study addressing the root system of T . koksaghyz to enhance the agronomic performance.

Twenty Years of Progress in Physiological and Biochemical Investigation of RALF Peptides

“…Interestingly, in a different study, atralf1mutant lines did not show any phenotypic difference from control plants when exposed to high salt conditions, and AtRALF1-overexpressors showed increased tolerance to salt (Feng et al, 2018). However, contrasting results for AtRALF-treated plants or for plants in which endogenous levels of expression are genetically manipulated have been reported (Wieghaus et al, 2019). CONCLUSION The initial biochemical screening for extracellular alkalinization activity led to the discovery of the first RALF peptide nearly twenty years ago.…”

Comparative Transcriptome Analysis in Taraxacum koksaghyz to Identify Genes that Determine Root Volume and Root Length

“…Suitable markers have not yet been identified in T. koksagyhz . Most studies thus far have focused on dandelion metabolism ( Schmidt et al, 2010 ; Epping et al, 2015 ; Pütter et al, 2017 ; Stolze et al, 2017 ; Niephaus et al, 2019 ) whereas few have considered growth characteristics ( Munt et al, 2012 ; Wieghaus et al, 2019 ) or field trials ( Arias et al, 2016a ; Kreuzberger et al, 2016 ; Eggert et al, 2018 ; Keener et al, 2018 ). Most of the relevant studies have aimed to improve yields or gain knowledge about agronomic performance.…”

“…Root growth is influenced by internal and external factors, particularly the interactions between phytohormones such as brassinosteroids ( Roddick et al, 1993 ; Clouse et al, 1996 ), jasmonate ( Dathe et al, 1981 ; Staswick et al, 1992 ) and auxins ( Chadwick and Burg, 1967 ), as well as various signaling peptides ( Yamada and Hsiao, 2021 ). In T. koksaghyz , only the influence of the small signaling peptide TkRALF1 has been investigated thus far ( Wieghaus et al, 2019 ). Little is known about the hormonal response to environmental conditions such as phosphorous and nitrogen availability in the rhizosphere, the root microbiome, or abiotic stresses such as water deprivation.…”

Functional Studies of Plant Latex as a Rich Source of Bioactive Compounds: Focus on Proteins and Alkaloids

“…Moreover, the inulin levels were higher in the knockouts whereas rubber levels were lower. Lower rubber content was compensated for with a higher dry weight of modified roots, such as the total yield per plant of inulin and rubber, which were much higher in knockout plants than in control [179]. It was shown that modification of gene TkRALFL1 can be used in subsequent breeding of profitable new dandelion varieties.…”