Phosphorus (P) is one of the macronutrients that is essential for plant growth and development. Anoectochilus roxburghii (Wall.) Lindl., an important orchid species, often encounters low-phosphorus stress during cultivation. Strigolactones (SLs) or their derivatives have recently been defined as novel plant hormones that regulate plant root development. However, it remains unclear whether SLs mediate root growth in response to phosphorus deficiency in A. roxburghii. In this study, the responses of A. roxburghii under P deficiency condition to different levels of SLs were investigated. The results demonstrated that the inhibition effect of low-phosphorus stress on plant growth in A. roxburghii significantly alleviated by SLs application, especially 0.1 mu mol L-1 of SL. The group treated with SL exhibited higher root elongation and lower levels of reactive oxygen species, as well as significantly increased soluble protein content and malonaldehyde. Furthermore, the SL treatment down-regulated the expression of several phosphorus-responsive genes, such as ArPHT6 and ArAP5, suggesting that SLs may promote phosphorus uptake or utilization to mitigate low-phosphorus stress. These findings provide an important new insights into the action mechanisms of SLs' in response to low-phosphorus stress and offer potential application value for cultivation and production of A. roxburghii. Future research will focus on exploring the molecular mechanism between SLs and phosphorus uptake.

Strigolactones (SLs) are plant hormones that regulate shoot branching. In addition, SLs act as compounds that stimulate the germination of root parasitic weeds, such as Striga spp. and Orobanche spp., which cause significant damage to agriculture worldwide. Thus, SL agonists have the potential to induce suicidal germination, thereby reducing the seed banks of root parasitic weeds in the soil. Particularly, phenoxyfuranone-type SL agonists, known as debranones, exhibit SL-like activity in rice and Striga hermonthica. However, little is known about their effects on Orobanche spp. In this study, we evaluated the germination-inducing activity of debranones against Orobanche minor. Analysis of structure-activity relationships revealed that debranones with electron-withdrawing substituents at the 2,4- or 2,6-position strongly induced the germination of Orobanche minor. Lastly, biological assays indicated that 5-(2-fluoro-4-nitrophenoxy)-3-methylfuran-2(5H)-one (test compound 61) induced germination to a comparable or even stronger extent than GR24, a well-known synthetic SL. Altogether, our data allowed us to infer that this enhanced activity was due to the recognition of compound 61 by the SLs receptor, KAI 2d, in Orobanche minor.

Strigolactones (SLs), the newest group of phytohormones, are involved in a wide range of functions, including the regulation of plant growth and physiology. Besides, emerging evidence suggests that SLs also participate in the promotion of plant environmental stress resilience through mediation of different metabolic genes/pathways. However, thus far little is known about SL-mediated transcriptional changes in rice (Oryza sativa), compared to other model plants. To meet this objective, we analyzed the RNA-seq-based comparative transcriptome data sets of rice SL-deficient dwarf l7 (d17) mutant line and its respective wild-type (WT), obtained from the National Center for Biotechnology Information GenBank. Both, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed, in order to identify genes/pathways which function downstream of SLs. With respect to the WT, a large number of functional GO terms, mainly stress-associated terms such as 'response to stress', 'response to stimulus', 'response to chemical', 'response to oxidative stress' and 'reactive oxygen species metabolic process' were significantly suppressed in the d17 mutant plants. In addition, KEGG metabolic pathways such as cvaline, leucine and isoleucine degradation', 'plant hormone signal transduction', 'galactose metabolism', 'fatty acid degradation' and 'phenylalanine metabolism' were also remarkably undermined in the d17 lines relative to the WT. These results imply a possible involvement of rice SLs in the regulation of distinct stress-related metabolic genes/pathways, which may function in environmental stress tolerance of plants. Taken together, the study provides new opportunities to broaden our limited understanding of SL-regulated downstream pathways, especially in rice.