Cloning and Expression of Gene Responsible for High-Tillering Dwarf Phenotype in Indica Rice Mutant gsor23

High-tillering dwarf mutant gsor23 was generated from an indica rice variety Indica9 radiatied by γ-ray. Genetic analysis showed that this phenotype was controlled by one single recessive gene, which was mapped within a physical distance of 386 kb between two insertion-deletion (InDel) markers C1-WT2 and C1-WT4 on the long arm of chromosome 1. There is a known gene D10 within this region, the mutation of which causes high-tillering in rice. Sequence analysis of the D10 allele in gsor23 revealed that the base cytosine (C) at the 404^th position in the coding region was deleted, which would cause frameshift mutation after the 134^th amino acids. The mutation site and indica background of gsor23 were different from the previously reported japonica mutants d10-1 and d10-2. Therefore, gsor23 is a novel allelic mutant of D10 which encodes the carotenoid-cleaving dioxygenase 8 (CCD8), a key enzyme involved in the biosynthesis of the new plant hormone strigolactones (SLs). After treatment with GR24, a synthetic analogue of SLs, the high-tillering phenotype of gsor23 was restored to normal. Real-time RT-PCR analysis showed that D10 expression was high in roots, but low in leaves. Compared with the wild type Indica9, the expression of the SL biosynthesis gene D10 was upregulated, while genes likely involved in the SL signal transduction pathway such as D3 and D14 were down-regulated in the gsor23 mutant.     

Synthesis of strigolactones,a strategic account

Strigolactones (SLs) constitute a new class of plant hormones that have received growing interest in recent years. They firstly became known as signalling molecules for host recognition by parasitic plants, and for symbiosis of plants with arbuscular mycorrhizal fungi. Furthermore, they are involved in numerous physiological processes in plants, such as the regulation of plant architecture and the response to abiotic factors. SLs are produced by plants in extremely low quantities, and they may be unstable during the purification process. Therefore, their total synthesis is highly relevant for confirming the structures assigned on the basis of spectroscopic and other physical data. A second important theme in SL research is the design and synthesis of SL analogues that have a simplified structure while still featuring the essential bioproperties. This review summarises the strategy and synthesis of naturally occurring SLs, and the design and synthesis of SL analogues with appreciable bioactivity. © 2015 Society of Chemical Industry     

Regulation of biosynthesis,perception, and functions of strigolactones for promoting arbuscular mycorrhizal symbiosis and managing root parasitic weeds

Strigolactones (SLs) are carotenoid‐derived plant secondary metabolites that play important roles in various aspects of plant growth and development as plant hormones, and in rhizosphere communications with symbiotic microbes and also root parasitic weeds. Therefore, sophisticated regulation of the biosynthesis, perception and functions of SLs is expected to promote symbiosis of beneficial microbes including arbuscular mycorrhizal (AM) fungi and also to retard parasitism by devastating root parasitic weeds. We have developed SL mimics with different skeletons, SL biosynthesis inhibitors acting at different biosynthetic steps, SL perception inhibitors that covalently bind to the SL receptor D14, and SL function inhibitors that bind to the serine residue at the catalytic site. In greenhouse pot tests, TIS108, an azole‐type SL biosynthesis inhibitor effectively reduced numbers of attached root parasites Orobanche minor and Striga hermonthica without affecting their host plants; tomato and rice, respectively. AM colonization resulted in weak but distinctly enhanced plant resistance to pathogens. SL mimics can be used to promote AM symbiosis and to reduce the application rate of systemic‐acquired resistance inducers which are generally phytotoxic to horticultural crops. © 2019 Society of Chemical Industry     

Suicidal germination for parasitic weed control

Parasitic weeds of the genera Striga and Orobanche spp. cause severe yield losses in agriculture, especially in developing countries and the Mediterranean. Seeds of these weeds germinate by a chemical signal exuded by the roots of host plants. The radicle thus produced attaches to the root of the host plant, which can then supply nutrients to the parasite. There is an urgent need to control these weeds to ensure better agricultural production. The naturally occurring chemical signals are strigolactones (SLs), e.g. strigol and orobanchol. One option to control these weeds involves the use of SLs as suicidal germination agents, where germination takes place in the absence of a host. Owing to the lack of nutrients, the germinated seeds will die. The structure of natural SLs is too complex to allow multigram synthesis. Therefore, SL analogues are developed for this purpose. Examples are GR24 and Nijmegen‐1. In this paper, the SL analogues Nijmegen‐1 and Nijmegen‐1 Me were applied in the field as suicidal germination agents. Both SL analogues were formulated using an appropriate EC‐approved emulsifier (polyoxyethylene sorbitol hexaoleate) and applied to tobacco (Nicotiana tabacum L.) fields infested by Orobanche ramosa L. (hemp broomrape), following a strict protocol. Four out of 12 trials showed a reduction in broomrape of ≥95%, two trials were negative, two showed a moderate result, one was unclear and in three cases there was no Orobanche problem in the year of the trials. The trial plots were ca 2000 m²; half of that area was treated with stimulant emulsion, the other half was not treated. The optimal amount of stimulant was 6.25 g ha^?1. A preconditioning prior to the treatment was a prerequisite for a successful trial. In conclusion, the suicidal germination approach to reducing O. ramosa in tobacco fields using formulated SL analogues was successful. Two other options for weed control are discussed: deactivation of stimulants prior to action and biocontrol by Fusarium oxysporum. © 2016 Society of Chemical Industry     

独脚金内酯调控植物分枝的研究进展

高等植物株形的形成受外界环境、遗传以及植物激素等多因素的影响。植物激素对调控植物地上部分枝起着重要作用,除公认调控植物分枝的生长素和细胞分裂素以外,独脚金内酯是一种新被发现的调控植物分枝的激素。对独脚金内酯调控植物分枝及其与生长素、细胞分裂素协同作用的分子机理进行了综述,并对其在园艺方面所具有的潜在应用价值进行了展望。     

Identification and Cloning of Tillering-Related Genes OsMAX1 in Rice

Tillering is an important agronomic trait which has a direct impact on plant type and grain yield. Strigolactones are a class of important phytohormones regulating rice tillering. ATMAX1 is an important gene involved in strigolactone biosynthesis through encoding the protein P450 in Arabidopsis. Based on sequence BLASTp, we identified five homologous genes of ATMAX1 in rice, i.e., OsMAX1a, OsMAX1b, OsMAX1c, OsMAX1d and OsMAX1e. Among them, OsMAX1a and OsMAX1e showed stable and high expression in rice tissues. In addition, we observed that Os MAX1a and OsMAX1e can rescue the branched phenotype and the influences caused by MAX1 mutation in Arabidopsis. Moreover, the expression of OsMAX1a and OsMAX1e can respond to phosphate deficiency and different phytohormones, especially GR24, a strigolactone analogue. Therefore, it is concluded that Os MAX1a and OsMAX1e are involved in the biosynthesis of strigolactones and regulated rice tillering.