Tiller Bud Outgrowth Research Articles

Sugar as a key component of the shoot branching regulation network.

This article comments on: Photosynthetic leaf area modulates tiller bud outgrowth in sorghum

Photosynthetic leaf area modulates tiller bud outgrowth in sorghum.

Shoot branches or tillers develop from axillary buds. The dormancy versus outgrowth fates of buds depends on genetic, environmental and hormonal signals. Defoliation inhibits bud outgrowth indicating the role of leaf-derived metabolic factors such as sucrose in bud outgrowth. In this study, the sensitivity of bud outgrowth to selective defoliation was investigated. At 6 d after planting (6 DAP), the first two leaves of sorghum were fully expanded and the third was partially emerged. Therefore, the leaves were selectively defoliated at 6 DAP and the length of the bud in the first leaf axil was measured at 8 DAP. Bud outgrowth was inhibited by defoliation of only 2 cm from the tip of the second leaf blade. The expression of dormancy and sucrose-starvation marker genes was up-regulated and cell cycle and sucrose-inducible genes was down-regulated during the first 24 h post-defoliation of the second leaf. At 48 h, the expression of these genes was similar to controls as the defoliated plant recovers. Our results demonstrate that small changes in photosynthetic leaf area affect the propensity of tiller buds for outgrowth. Therefore, variation in leaf area and photosynthetic activity should be included when integrating sucrose into models of shoot branching.

QTL analysis in multiple sorghum populations facilitates the dissection of the genetic and physiological control of tillering.

A QTL model for the genetic control of tillering in sorghum is proposed, presenting new opportunities for sorghum breeders to select germplasm with tillering characteristics appropriate for their target environments. Tillering in sorghum can be associated with either the carbon supply-demand (S/D) balance of the plant or an intrinsic propensity to tiller (PTT). Knowledge of the genetic control of tillering could assist breeders in selecting germplasm with tillering characteristics appropriate for their target environments. The aims of this study were to identify QTL for tillering and component traits associated with the S/D balance or PTT, to develop a framework model for the genetic control of tillering in sorghum. Four mapping populations were grown in a number of experiments in south east Queensland, Australia. The QTL analysis suggested that the contribution of traits associated with either the S/D balance or PTT to the genotypic differences in tillering differed among populations. Thirty-four tillering QTL were identified across the populations, of which 15 were novel to this study. Additionally, half of the tillering QTL co-located with QTL for component traits. A comparison of tillering QTL and candidate gene locations identified numerous coincident QTL and gene locations across populations, including the identification of common non-synonymous SNPs in the parental genotypes of two mapping populations in a sorghum homologue of MAX1, a gene involved in the control of tiller bud outgrowth through the production of strigolactones. Combined with a framework for crop physiological processes that underpin genotypic differences in tillering, the co-location of QTL for tillering and component traits and candidate genes allowed the development of a framework QTL model for the genetic control of tillering in sorghum.

Exogenous hormonal application improves grain yield of wheat by optimizing tiller productivity

The compositions of tillers, which are directly related to the grain yield, markedly affect the structure and quality of a wheat population. Constructing a rational population structure based on the superior tillers also enhances the yield potential of wheat. However, information on the non-uniformity in the productive capacity of tillers in wheat and the lack of effective measures to regulate the population structure is insufficient. In the present study, two winter wheat cultivars, Shannong15 (SN15) and Shannong8355 (SN8355), were used to (1) evaluate the differences in productive capacity among tillers in wheat, (2) analyze the underlying mechanisms between endogenous hormone and wheat tiller production by exogenous hormones, and (3) investigate the effects of exogenous hormones on the grain yield of wheat. Results showed that low-position tillers (early initiated tillers) exhibited a higher yield per spike than high-position tillers (late-initiated tillers) in both cultivars. Cluster analysis showed that tillers of SN15 were classified into two groups: the superior tiller group, which included the main stem (0), the first primary tiller (I), and the second primary tiller (II); and the inferior tiller group, which included the third primary tiller (III) and the first secondary tiller (I-p). The tillers of SN8355 were classified into three groups: superior tiller group (0 and I), intermediate tiller group (II and III) and inferior tiller group (I-p). Indole-3-acetic acid (IAA) and zeatin (ZT) exhibited important functions in regulating the growth of tillers. Exogenous hormones regulated the growth of wheat tiller buds by affecting the contents of IAA and ZT as well as the ratios of IAA to ZT and abscisic acid (ABA) to ZT in the tiller nodes, thereby regulating the growth of tillers. Furthermore, the external application of IAA, gibberellic acid (GA3), and ABA evidently reduced the number of stems per square meter at wintering and jointing stages, which could promote the accumulation of single-stem biological yield. The wheat plants in the IAA, GA3, and ABA groups yielded more grains and higher grain weight than those in the control group; as a result, grain yield increased. These results suggested that the tiller composition of a wheat population could be restructured (based on the superior tiller) by inhibiting the growth of inferior tillers induced by external IAA, GA, and ABA treatments to enhance the yield potential of wheat.

THIS1 is a putative lipase that regulates tillering, plant height, and spikelet fertility in rice

Proper branching and successful reproductive growth is of great importance for rice productivity. Substantial progress has been made in uncovering the molecular mechanisms underlying tillering control and spikelet sterility. However, rice tillering is developmentally controlled, and how it is regulated coordinately with reproductive growth remains unclear. This study characterized a rice mutant, the most obvious phenotypes of which are high tillering, reduced height, and infertile spikelets (named this1). Similarly to the high tiller number and dwarf mutants in rice, the increased tiller number of this1 plants is ascribed to the release of tiller bud outgrowth rather than to increased tiller bud formation. In the this1 mutant, however, the accelerated rate of branching was delayed until the stem elongation stage, while other mutants lost the ability to control branching at all developmental stages. The seed-setting rate of this1 was less than half that of the wild type, owing to defects in pollen maturation, anther dehiscence, and flower opening. Histological analyses showed that the mutation in this1 resulted in anisotropic cell expansion and cell division. Using a map-based cloning approach, This1 was found to encode a class III lipase. Homology searches revealed that THIS1 is conserved in both monocots and eudicots, suggesting that it plays fundamental role in regulating branch and spikelet fertility, as well as other aspects of developmental control. The relative change in expression of marker genes highlighted the possibility that This1 is involved in phytohormone signalling pathways, such as those for strigolactone and auxin. Thus, This1 provides joint control between shoot branching and reproductive development.

Genome-Wide Binding Analysis of the Transcription Activator IDEAL PLANT ARCHITECTURE1 Reveals a Complex Network Regulating Rice Plant Architecture

Ideal plant architecture1 (IPA1) is critical in regulating rice (Oryza sativa) plant architecture and substantially enhances grain yield. To elucidate its molecular basis, we first confirmed IPA1 as a functional transcription activator and then identified 1067 and 2185 genes associated with IPA1 binding sites in shoot apices and young panicles, respectively, through chromatin immunoprecipitation sequencing assays. The Squamosa promoter binding protein-box direct binding core motif GTAC was highly enriched in IPA1 binding peaks; interestingly, a previously uncharacterized indirect binding motif TGGGCC/T was found to be significantly enriched through the interaction of IPA1 with proliferating cell nuclear antigen promoter binding factor1 or promoter binding factor2. Genome-wide expression profiling by RNA sequencing revealed IPA1 roles in diverse pathways. Moreover, our results demonstrated that IPA1 could directly bind to the promoter of rice teosinte branched1, a negative regulator of tiller bud outgrowth, to suppress rice tillering, and directly and positively regulate dense and erect panicle1, an important gene regulating panicle architecture, to influence plant height and panicle length. The elucidation of target genes of IPA1 genome-wide will contribute to understanding the molecular mechanisms underlying plant architecture and to facilitating the breeding of elite varieties with ideal plant architecture.

Selective Mimics of Strigolactone Actions and Their Potential Use for Controlling Damage Caused by Root Parasitic Weeds

Strigolactones (SLs) are a novel class of plant hormones and rhizosphere communication signals, although the molecular mechanisms underlying their activities have not yet been fully determined. Nor is their application in agriculture well developed. The importance of plant hormone agonists has been demonstrated in both basic and applied research, and chemicals that mimic strigolactone functions should greatly facilitate strigolactone research. Here, we report our discovery of a new phenoxyfuranone compound, 4-Br debranone (4BD), that shows similar activity to that of the major strigolactone (SL) analog GR24 in many aspects of a biological assay on plants. 4BD strongly inhibited tiller bud outgrowth in the SL-deficient rice mutant d10 at the same concentration as GR24, with no adverse effects, even during prolonged cultivation. This result was also observed in the Arabidopsis thaliana SL-deficient mutants max1, max3, and max4. However, the application of 4BD to the Arabidopsis SL-insensitive mutant max2 induced no morphological changes in it. The expression of SL biosynthetic genes was also reduced by 4BD treatment, probably via negative feedback regulation. However, in a seed germination assay on Striga hermonthica, a root parasitic plant, 4BD showed far less activity than GR24. These results suggest that 4BD is the first plant-specific strigolactone mimic.

Control of Tiller Growth of Rice by OsSPL14 and Strigolactones, Which Work in Two Independent Pathways

The architecture of rice is greatly influenced by the growth of tillers, i.e. vegetative shoot branches. OsSPL14, a member of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, and strigolactones (SLs) are known to suppress outgrowth of tiller buds. OsSPL14 also regulates panicle development. We show that OsSPL14 mRNA accumulates in leaf primordia during the vegetative phase and in the primordia of bracts, or modified leaves, in the panicles, but not in the meristems. OsSPL14 is a target of miR156, and accumulation of OsSPL14 transcripts is negatively regulated by miR156. The enhancement of the expression level of OsSPL14 by the introduction of the mOsSPL14 gene, in which the miR156 cleavage site is mutated, resulted in an increase in the plastochron, an acceleration of flowering and a decrease in tiller number in the wild type and in dwarf10-2, an SL-deficient mutant. Our analysis suggests that OsSPL14 and SLs function in parallel pathways to suppress tiller growth. SLs exuded from roots trigger germination of root parasitic plants that can cause severe damage to crop productivity. SL-deficient mutants, however, exhibit an excess branching phenotype which is usually undesirable for productivity. Our results indicate that OsSPL14 can be used to manipulate the branching patterns of SL-deficient mutants. We also confirmed that this strategy is applicable to Arabidopsis. A greater understanding of the OsSPL14 and SL pathways and their interactions may help in the production of root parasite-resistant crops.

Inhibition of tiller bud outgrowth in the tin mutant of wheat is associated with precocious internode development.

Tillering (branching) is a major yield component and, therefore, a target for improving the yield of crops. However, tillering is regulated by complex interactions of endogenous and environmental signals, and the knowledge required to achieve optimal tiller number through genetic and agronomic means is still lacking. Regulatory mechanisms may be revealed through physiological and molecular characterization of naturally occurring and induced tillering mutants in the major crops. Here we characterize a reduced tillering (tin, for tiller inhibition) mutant of wheat (Triticum aestivum). The reduced tillering in tin is due to early cessation of tiller bud outgrowth during the transition of the shoot apex from the vegetative to the reproductive stage. There was no observed difference in the development of the main stem shoot apex between tin and the wild type. However, tin initiated internode development earlier and, unlike the wild type, the basal internodes in tin were solid rather than hollow. We hypothesize that tin represents a novel type of reduced tillering mutant associated with precocious internode elongation that diverts sucrose (Suc) away from developing tillers. Consistent with this hypothesis, we have observed upregulation of a gene induced by Suc starvation, downregulation of a Suc-inducible gene, and a reduced Suc content in dormant tin buds. The increased expression of the wheat Dormancy-associated (DRM1-like) and Teosinte Branched1 (TB1-like) genes and the reduced expression of cell cycle genes also indicate bud dormancy in tin. These results highlight the significance of Suc in shoot branching and the possibility of optimizing tillering by manipulating the timing of internode elongation.

The Positional Effects of Auxin and Cytokinin on the Regulation of Rice Tiller Bud Growth

ABSTRACTAuxin and cytokinin (CTK) play important roles in the regulation of rice (Oryza sativa L.) tiller bud growth. Auxin inhibits bud growth and CTK promotes growth; however, little is known about the positional effects of these hormones in the regulation of rice tiller bud growth. In the present study, indole‐3‐acetic acid (IAA) and 6‐benzylaminopurine (6‐BA) (a synthetic CTK) were applied to different leaves and roots at the tillering and heading stages of rice development, and the growth of rice tiller buds on the unelongated and elongated internodes was measured. Additionally, hormonal variations of the plants were examined and recorded. The objectives of the present study were to investigate the positional effects of auxin and CTK on the regulation of rice tiller bud growth. The results indicate that IAA has a notable positional effect on the regulation of rice tiller bud growth, and the positional effect of IAA was closely related to its polar transport. An increase in leaf IAA levels inhibited the growth of tiller buds located at unelongated nodes; however, growth of tiller buds at elongated nodes was inhibited only when IAA levels were increased in the upper‐stem leaves or the leaves at which the tiller bud was located. Contrary to IAA, 6‐BA had no positional effect on rice tiller bud growth. Application of 6‐BA to different leaves and roots significantly promoted the growth of rice tiller buds at both unelongated and elongated nodes.

Effect of Plant Growth Regulators on the Growth of Rice Tiller Bud and the Changes of Endogenous Hormones

Hormones have substantial effect on tiller bud growth of rice. However, little is known on the relation between endogenous hormonal changes and the growth of rice tiller bud induced by exogenous hormones. In present study, two rice cultivars (Yangdao 6 and Nanjing 44) were used to investigate the effect of exogenous ABA, GA3, and NAA on tiller bud outgrowth and the changes of endogenous hormones. The results showed that exogenous GA3 and NAA completely inhibited the tiller bud growth, while applied ABA did not, but ABA slowed the growth rate of it. Both exogenous GA3 and NAA increased the ABA contents and decreased the Z+ZR contents in tiller node and tiller bud, and exogenous GA3 increased the IAA content in tiller node, and IAA and Z+ZR changed earlier than ABA. In conclusion, IAA and Z+ZR may play key roles in regulating the growth of rice tiller bud, while ABA may not, although ABA can affect the growth velocity of tiller bud; the effect of exogenous hormones on rice tiller bud growth is through regulating the contents of ABA, IAA, and CTK in plants.

New branching inhibitors and their potential as strigolactone mimics in rice

Strigolactones (SLs) are rhizosphere communication chemicals. Recent studies of highly branched mutants revealed that SL or its metabolites work as a phytohormone to inhibit shoot branching. When SLs are exogenously applied to the rice d10-1 mutant that has a highly branched phenotype caused by a defect in the SL biosynthesis gene (CCD8), they inhibit tiller bud outgrowth (branching in rice) of the mutant. We focused our attention on the SL function as a phytohormone and tried to find new chemicals mimicking the hormonal action of SL by screening chemicals that inhibit branching of rice d10-1 mutant. Fortunately, we found 5-(4-chlorophenoxy)-3-methylfuran-2(5H)-one (3a) as a new chemical possessing SL-like activity against the rice d10-1 mutant. Then, we prepared several derivatives of 3a (3b-3k) to examine their ability to inhibit shoot branching of rice d10-1. These derivatives were synthesized by a one-pot coupling reaction between phenols and halo butenolide to give 5-phenoxy 3-methylfuran-2(5H)-one (3) derivatives, which possess a common substructure with SLs. Some of the derivatives showed SL-like activity more potently than GR24, a typical SL derivative, in a rice assay. As SLs also show activity by inducing seed germination of root parasitic plants, the induction activity of these derivatives was also evaluated. Here we report the structure-activity relationships of these compounds.

Effects of external ABA, GA3 and NAA on the tiller bud outgrowth of rice is related to changes in endogenous hormones

Hormones play an important role in regulating the growth of rice tiller buds. However, little is known about the hormonal changes that occur during tiller bud growth and the mechanism of hormonal regulation of tiller bud growth. Here, two rice cultivars, Yangdao 6 (Indica) and Nanjing 44 (Japonica), were used to investigate the changes in plant hormones during tiller bud growth and the mechanism that underlies the hormonal regulation of tiller bud growth. In the present study, panicles were removed after heading to stimulate the growth of dormant tiller buds located at the elongated upper internodes. At the same time, external abscisic acid (ABA), gibberellic acid (GA3) and α-naphthalene acetic acid (NAA) were applied. The results demonstrated that auxin and cytokinin (CTK) play important and different roles in the regulation of tiller bud growth. Auxin in the nodes inhibits tiller bud growth, while CTK is transferred to the tiller buds to promote growth. The inhibitory effects of GA3 and NAA on tiller bud growth are mainly due to the control of the indole-3-acetic acid (IAA) or CTK contents in plants. As opposed to auxin and CTK, the ABA contents in nodes and tiller buds remained unchanged before tiller bud growth after panicle removal. Meanwhile, external ABA application only slightly slowed the growth of the tiller buds, suggesting that ABA may not be a key regulator of tiller bud growth. These results indicate that auxin, CTK and ABA together likely play roles in the regulation of tiller bud growth.

Effect of Plant Growth Regulators on Growth of Rice Tiller Bud and Changes of Endogenous Hormones

The objectives of this study were to investigate the changes in plant hormones during tiller bud growing in rice ( Oryza sativa L.) and the mechanism that underlies the effect of hormonal regulation on tiller bud growth. Rice cultivars Yangdao 6 ( indica) and Nanjing 44 ( japonica) were used to investigate the effects of exogenous abscisic acid (ABA, 50 mg L −1), gibberellic acid 3 (GA 3, 50 mg L −1), and α-naphthalene acetic acid (NAA, 50 mg L −1) on tiller bud outgrowth and the changes of endogenous hormones. After foliar spray of the exogenous hormones, the tiller bud growth was completely inhibited in treatments of GA 3 and NAA applies; but exogenous ABA application slowed down the growth rate of tiller bud. Both exogenous GA 3 and NAA increased the ABA contents in tiller node and tiller bud and decreased the zeatin + zeatin riboside (Z+ZR) contents. Exogenous GA 3 increased the IAA content in tiller node; besides, the variation of IAA and Z+ZR occurred earlier than that of ABA. Suggestively, these 3 endogenous hormones are closely associated with tiller bud growth, of which only IAA and Z+ZR play key roles, although ABA can affect the growth velocity of tiller bud. Exogenous hormones regulate tiller bud growth through changing the contents of endogenous ABA, IAA, and Z+ZR in rice plant.

Effects of Nitrogen and 6‐Benzylaminopurine on Rice Tiller Bud Growth and Changes in Endogenous Hormones and Nitrogen

ABSTRACTIn the present study, 40 mg L−1 N (NH treatment) and 20 mg L−1 6‐benzylaminopurine (6‐BA; BA treatment) were used to stimulate tiller bud growth in rice (Oryza sativa L.). The hormone changes in the tiller nodes and tiller buds and the N levels in the leaf blades, leaf sheaths, and tiller nodes were measured. The results indicate that N and 6‐BA promoted tiller bud germination and increased the indole‐3‐acetic acid (IAA) and zeatin (Z) plus zeatin riboside (ZR) levels in tiller buds and tiller nodes but decreased the abscisic acid (ABA) levels in tiller buds. Before tiller bud germination, the IAA and Z plus ZR levels increased but the ABA did not change, suggesting that IAA and Z plus ZR but not ABA may be the key regulators of tiller bud growth. From 4 d posttreatment, the tiller bud growth of the BA‐treated plants markedly slowed but the buds of the NH‐treated plants continued to grow quickly. We also found that the N levels in the leaf blades, leaf sheaths, and tiller nodes of the NH‐treated plants increased significantly as compared to those of the control plants (the plants treated with 10 mg L−1 N). However, no significant differences in N levels were observed between the plants of BA and control treatments. This study suggests that N may regulate tiller bud growth in two ways: by regulating N metabolism and regulating endogenous hormones. External 6‐BA promoted tiller bud germination by regulating endogenous hormones, but tiller bud growth was not maintained because it could not increase the N levels in the plants.

Contribution of Strigolactones to the Inhibition of Tiller Bud Outgrowth under Phosphate Deficiency in Rice

Strigolactones (SLs) or SL-derived metabolite(s) have recently been shown to act as endogenous inhibitors of axillary bud outgrowth. SLs released from roots induce hyphal branching of arbuscular mycorrhizal (AM) fungi that facilitate the uptake of inorganic nutrients, such as phosphate (Pi) and nitrate, by the host plants. Previous studies have shown that SL levels in root exudates are highly elevated by Pi starvation, which might contribute to successful symbiosis with AM fungi in the rhizosphere. However, how endogenous SL levels elevated by Pi starvation contribute to its hormonal action has been unknown. Here, we show that tiller bud outgrowth in wild-type rice seedlings is inhibited, while root 2′-epi-5-deoxystrigol (epi-5DS) levels are elevated, in response to decreasing Pi concentrations in the media. However, the suppression of tiller bud outgrowth under Pi deficiency does not occur in the SL-deficient and -insensitive mutants. We also show that the responsiveness to exogenous SL is slightly increased by Pi deficiency. When Pi-starved seedlings are transferred to Pi-sufficient media, tiller bud outgrowth is induced following a decrease in root epi-5DS levels. Taken together, these results suggest that elevated SL levels by Pi starvation contribute to the inhibition of tiller bud outgrowth in rice seedlings. We speculate that SL plays a dual role in the adaptation to Pi deficiency; one as a rhizosphere signal to maximize AM fungi symbiosis for improved Pi acquisition and the other as an endogenous hormone or its biosynthetic precursor to optimize shoot branching for efficient Pi utilization.

A New Lead Chemical for Strigolactone Biosynthesis Inhibitors

Several triazole-containing chemicals have previously been shown to act as efficient inhibitors of cytochrome P450 monooxygenases. To discover a strigolactone biosynthesis inhibitor, we screened a chemical library of triazole derivatives to find chemicals that induce tiller bud outgrowth of rice seedlings. We discovered a triazole-type chemical, TIS13 [2,2-dimethyl-7-phenoxy-4-(1H-1,2,4-triazol-1-yl)heptan-3-ol], which induced outgrowth of second tiller buds of wild-type seedlings, as observed for non-treated strigolactone-deficient d10 mutant seedlings. TIS13 treatment reduced strigolactone levels in both roots and root exudates in a concentration-dependent manner. Co-application of GR24, a synthetic strigolactone, with TIS13 canceled the TIS13-induced tiller bud outgrowth. Taken together, these results indicate that TIS13 inhibits strigolactone biosynthesis in rice seedlings. We propose that TIS13 is a new lead compound for the development of specific strigolactone biosynthesis inhibitors.

Effects of air supply on the growth of tiller buds in floating rice.

Effects of air supply on the growth of tiller buds in floating rice.

Simulation of wheat growth and development based on organ-level photosynthesis and assimilate allocation

Intimate relationships exist between form and function of plants, determining many processes governing their growth and development. However, in most crop simulation models that have been created to simulate plant growth and, for example, predict biomass production, plant structure has been neglected. In this study, a detailed simulation model of growth and development of spring wheat (Triticum aestivum) is presented, which integrates degree of tillering and canopy architecture with organ-level light interception, photosynthesis, and dry-matter partitioning. An existing spatially explicit 3D architectural model of wheat development was extended with routines for organ-level microclimate, photosynthesis, assimilate distribution within the plant structure according to organ demands, and organ growth and development. Outgrowth of tiller buds was made dependent on the ratio between assimilate supply and demand of the plants. Organ-level photosynthesis, biomass production, and bud outgrowth were simulated satisfactorily. However, to improve crop simulation results more efforts are needed mechanistically to model other major plant physiological processes such as nitrogen uptake and distribution, tiller death, and leaf senescence. Nevertheless, the work presented here is a significant step forwards towards a mechanistic functional-structural plant model, which integrates plant architecture with key plant processes.

Identification and characterization of HTD2: a novel gene negatively regulating tiller bud outgrowth in rice

Tiller number is highly regulated by controlling the formation of tiller bud and its subsequent outgrowth in response to endogenous and environmental signals. Here, we identified a rice mutant htd2 from one of the 15,000 transgenic rice lines, which is characterized by a high tillering and dwarf phenotype. Phenotypic analysis of the mutant showed that the mutation did not affect formation of tiller bud, but promoted the subsequent outgrowth of tiller bud. To isolate the htd2 gene, a map-based cloning strategy was employed and 17 new insertions-deletions (InDels) markers were developed. A high-resolution physical map of the chromosomal region around the htd2 gene was made using the F(2) and F(3) population. Finally, the gene was mapped in 12.8 kb region between marker HT41 and marker HT52 within the BAC clone OSJNBa0009J13. Cloning and sequencing of the target region from the mutant showed that the T-DNA insertion caused a 463 bp deletion between the promoter and first exon of an esterase/lipase/thioesterase family gene in the 12.8 kb region. Furthermore, transgenic rice with reduced expression level of the gene exhibited an enhanced tillering and dwarf phenotype. Accordingly, the esterase/lipase/thioesterase family gene (TIGR locus Os03g10620) was identified as the HTD2 gene. HTD2 transcripts were expressed mainly in leaf. Loss of function of HTD2 resulted in a significantly increased expression of HTD1, D10 and D3, which were involved in the strigolactone biosynthetic pathway. The results suggest that the HTD2 gene could negatively regulate tiller bud outgrowth by the strigolactone pathway.