Identification and molecular mapping of indica high‐tillering dwarf mutant htd4, a mild phenotype allelic mutant of D14 in rice (Oryza sativa L.)

Abstract

Metabolism of strigolactones (SLs) can improve the efficiency of nutrient use by regulating the development of roots and shoots in crops, making them an important research focus for molecular breeding. However, as a very important plant hormone, the molecular mechanism of SL signal transduction still remains largely unknown. In this study, we isolated an indica high-tillering dwarf mutant 4 (htd4), a spontaneous mutant of rice, from the restorer line Gui99. Mapping and sequencing analysis showed that htd4 was a novel allelic mutant of D14, in which a single base substitution forms a premature termination codon. Quantitative RT-PCR analyses revealed that expression levels of the genes D10, D17, D27, D3 and D14 increased significantly, while expression of D53 decreased in htd4, compared with the wild type. A subcellular localisation assay showed that the mutant of D14 in htd4 did not disturb the normal localisation of D14 proteins. However, a BiFC assay suggested that the mutant-type D14 could not interact with D3. Additionally, compared with other D14 allelic mutants, htd4 was the first mutant of D14 discovered in indica, and the differences in many yield traits such as plant height, seed-setting rate and grain sizes between htd4 and the wild type were less than those between other D14 allelic mutants and the wild type. Therefore, htd4 is considered a mild phenotype allelic mutant of D14. We conclude that the absence of functional D14 caused the high-tillering dwarf phenotype of htd4. Our results may provide vital information for research on D14 function and the application of htd4 in molecular breeding.

The Physiological Basis of Alfalfa Plant Height Establishment

“…The stem of a plant determines the vertical distribution of leaves, and the stem, as a "reservoir" for nutrient absorption and assimilation, largely determines the ability of the plant to photosynthesize. Tall culm materials have relatively long stem nodes and a uniform vertical distribution of leaf blades, and the upper and middle leaf blades receive sufficient light, thus accumulating a higher amount of photosynthetically active products than short culm materials, consistent with the results of a previous study [46]. At the individual and population levels, differences in the local light competition environment led to stronger negative feedback between the inputs to plant height and the consumption of photosynthetic products by small individuals within the cluster, i.e., asymmetric competition for light resources, and higher photosynthetic products favored plant growth and development, which significantly promoted plant height [47].…”

The Role of Dwarfing Traits in Historical and Modern Agriculture with a Focus on Rice

“…Furthermore, both d14 and d88 mutants display a larger number of shorter tillers with smaller panicles and seeds (Gao et al 2009). The spontaneous, mild phenotype mutant allele of D14, htd4, results from a nonsense mutation that causes a premature stop codon (Wang et al 2017). htd4 plants also display higher tiller number, dwarf stature, shorter internodes, and smaller panicles and leaves (Wang et al 2017).…”

“…The spontaneous, mild phenotype mutant allele of D14, htd4, results from a nonsense mutation that causes a premature stop codon (Wang et al 2017). htd4 plants also display higher tiller number, dwarf stature, shorter internodes, and smaller panicles and leaves (Wang et al 2017). Another D14 mutant, htd2, also shows high tillering, reduced height, and reduction in blade length and width, culm diameter, and panicle size (Liu et al 2009).…”

Phytohormone-Mediated Molecular Mechanisms Involving Multiple Genes and QTL Govern Grain Number in Rice

“…Another loss-of-function allelic mutant of D14, htd4, bears a large number of effective panicles per plant. However, traits like panicle length, number of grains per panicle, primary branch numbers, seed-setting rate, and 1,000grain weight are decreased in htd4 plants (Wang et al, 2017). Recently, a new loss-of-function allele of D14, i.e., dhta-34, has been identified, whose plants also show similar phenotypes (Liang et al, 2019).…”