Antibacterial Activity and Mechanisms of Ethanol Extracts from <i>Scutellaria baicalensis</i> Georgi and <i>Magnolia officinalis</i> against <i>Phytophthora nicotianae</i>

Phytophthora nicotianae causes substantial economic losses in most countries where tobacco is produced. At present, the control of P. nicotianae mainly depends on chemical methods, with considerable environmental and health issues. We investigated the effects of ethanol extracts from Scutellaria baicalensis Georgi (SBG) and Magnolia officinalis (MO). On mycelial growth, sporangium formation, and zoospore release of P. nicotianae. Both extracts inhibited the growth of P. nicotianae, with mycelial growth inhibition rates of 88.92% and 93.92%, respectively, at 40 mg/mL, and EC50 values of 5.39 and 5.74 mg/mL, respectively. The underlying mechanisms were the inhibition of sporangium formation, the reduction of zoospore number, and the destruction of the mycelium structure. At an SBG extract concentration of 16.17 mg/mL, the inhibition rates for sporangia and zoospores were 98.66% and 99.39%, respectively. At an MO extract concentration of 2.87 mg/mL, the production of sporangia and zoospores was completely inhibited. The hyphae treated with the two plant extracts showed different degrees of deformation and damage. Hyphae treated with SBG extract showed adhesion and local swelling, whereas treatment with MO extract resulted in broken hyphae. Mixture of the extracts resulted in a good synergistic effect.     

Inhibitory Effect of <i>N</i>, <i>N</i>-Dimethylhexadecylamine on the Growth of White-Rot Fungus <i>Trametes versicolor</i> (L.) in Wood

Wood is an organic material that is a source of carbon of organisms called Wood-decay fungi, and to preserve the wood, various toxic compounds to man and the environment have been used. To analyze the effect of N,N-Dimethylhexadecylamine (DMHDA) on wood attacked by the rotting fungus Trametes versicolor L. We used an in vitro system to expose the fungus T. versicolor to different concentrations of the DMHDA (50, 150 and 450 μM). We quantified the diameter of mycelial growth and laccase activity, also, under these experimental conditions we studied morphological details of the organisms using different scanning equipment including scanning electron microscopy. The growth of T. versicolor exposed to DMHDA for 60 days, showed a concentration-dependent dose behavior, also, the electron microscopy analysis revealed that the morphology and mycelial density was affected by the DMHDA, showing a formation of atypical morphological and thickener folds. Finally, the pieces of wood treated with DMHDA and exposed to the fungus had a lower mass loss, after a period of 60 days of exposure, the values obtained were 0.7, 1.0 and 0.5 g of mass lost for the control, LoC and LoDMHDA treatments respectively. Wood-rot fungi have represented economic losses worldwide, the strategies used have been supported by toxic compounds for the environment. The DMHDA both in the Petri dish system and as a wood preservative was shown to significantly inhibit the growth of T. versicolor.     

AM Fungi and <i>Piriformospora indica</i> Improve Plant Growth of <i>Pinus elliottii</i> Seedlings

Pinus elliottii is an exotic afforestation pine extensively distributed in southern parts of China. In order to understand whether endophytic fungi can affect seedling growth of P. elliottii, Piriformospora indica (Pi), Funnelifcrmis mosseae (Fm), and Diversispora tortuosa (Dt) were inoculated respectively, and the non-inoculated group was set as control. The growth indexes, the contents of soluble sugar and soluble protein, and plant endogenous hormone levels in the leaves of P. elliottii, were analyzed. The results showed that Fm, Dt and Pi colonized the P. elliottii roots to form mycorrhizal structure and chlamydospores arranged in beads respectively. Three fungal inoculants exhibited the stimulated growth responses, whilst Dt illustrated the most positive effect on plant height, single fresh weight, trunk diameter and root system structure, compared with the control. On the other hand, the soluble sugar and soluble protein contents were increased distinctively in mycorrhizal plants. The endogenous IAA, GA3, ZR contents were increased, while the ABA contents were reduced in mycorrhizal plants versus non-mycorrhizal plants. The fungi-induced endogenous hormone changes triggered plant growth improvement of P. elliottii seedlings. This research unraveled the positive effect of AM fungi and P. indica on growth of pine seedlings, while, more application of endophytic fungi to fields needs to be explored.     

Efficient Evergreen Plant Regeneration of <i>Cinnamomum japonicum</i> Sieb. through <i>in vitro</i> Organogenesis

Cinnamomum japonicum Sieb. is an excellent roadside tree and medicinal tree species with considerable ornamental and economic value. In this study, we successfully developed a large-scale micropropagation protocol for C. japonicum for the first time. Sterilized shoots were excised and used as explants for shoot induction on several basal media, supplemented with different concentrations of plant growth regulators (PGRs), such as Thidiazuron (TDZ), N⁶ -Benzyladenine (6-benzylaminopurine) (BA), α-naphthaleneacetic acid (NAA) and Gibberellic acid (GA₃). After comparison, the most efficient medium for shoot regeneration was 1/2 Murashige and Skoog (MS) medium containing 0.5 mg L^–1 BA, 0.05 mg L^–1 NAA and 0.2 mg L^–1 GA₃, which resulted in an average number of induced shoots per explant and shoot length of 5.2 and 1.62 cm at 28 d, respectively. Then, elongated adventitious shoots were transferred to induce roots. 86.7% of shoots was able to root on 1/2 MS medium supplemented with 0.5 mg L^–1 NAA and 0.1 mg L^–1 BA. The earliest rooting time observed was after 21 d and the average root length was up to 3.3 cm after 28 d. Our study shows that C. japonicum can be successfully regenerated through de novo organogenesis, which lays a foundation for future transformation research on this tree.     

First Report of <i>Fusarium striatum</i> Causing Root Rot Disease of <i>Panax notoginseng</i> in Yunnan,China

Panax notoginseng is a traditional Chinese medicinal plant. Root rot of P. notoginseng is one of the most serious diseases affecting P. notoginseng growth and causes wilted leaves, fewer lateral roots and rotten roots. Root rot is a soil-borne disease, and mainly occurs from June to August in Yunnan Province when the temperatures are high and the air is humid. In this study, the endophytic fungal genus Fusarium isolate E-2018.1.22-#3.2 was obtained from a P. notoginseng embryo. Fusarium isolate E-2018.1.22-#3.2 was identified as Fusarium striatum based on morphological characteristics and molecular analysis. The fungus was found to have conidiophores and macroconidia, and its ITS, LSU and TEF-1α genes shared 100%, 99.2% and 99% identities with the homologous genes of Fusarium striatum, respectively. Isolate F. striatum E-2018.1.22-#3.2 can cause root rot symptoms, including black, soft roots, fewer lateral roots and leaf wilt, in 93% of the experimental P. notoginseng plants, and could be re-isolated, fulfilling Koch’s postulates. When the P. notoginseng plants were treated with the fungicide pyraclostrobin, isolate F. striatum E-2018.1.22-#3.2 was unable to cause root rot. We have therefore demonstrated that F. striatum E-2018.1.22-#3.2 is able to cause root rot disease in P. notoginseng. This is the first report of root rot disease caused by F. striatum on P. notoginseng in China.     

<i>In vitro</i> Germination and Micropropagation of <i>Aconitum vilmorinianum</i>: An Important Medicinal Plant in China

Aconitum vilmorinianum, a well-known traditional Chinese herb, is recently being threatened by overexploitation and environment disturbance. This study was conducted to provide propagation methods through in vitro germination and explant cultivation. Germination was stimulated up to 66.00% on Murashige and Skoog (MS) medium containing 2.0 mg L⁻¹ 6-benzylaminopurine (BAP), 0.1 mg L⁻¹ 1-napthaleneacetic acid (NAA), and 30 g L⁻¹ sucrose. Three bacteria (Pantoea agglomerans, Erwinia persicina, and Pseudomonas tolaasii) would be responsible for consistent contamination during germination. The latter two were effectively eradicated after disinfected. The influence of explant types and hormone combinations on direct and indirect organogenesis was evaluated in the present work. The frequency of shoot induction from axillary bud explants was 100% on the MS fortified with 2.0 mg L⁻¹ BAP and 0.3 mg L⁻¹ NAA. Shoots multiplication was optimized on MS medium supplemented with 0.1 mg L⁻¹ thidiazuron (TDZ) and 0.1 mg L⁻¹ NAA. High callus induction percentage (96.67%) was obtained from stem segments on MS medium with 2.0 mg L⁻¹ 2,4-D, then successfully regenerated into shoots on MS medium in the presence of 0.1 mg L⁻¹ TDZ and 0.2 mg L⁻¹ NAA. The present work could be useful for the utilization and conservation of this valuable species.     

Estimation of Growth and Photosynthetic Performance of Two C₄ Species (<i>Pennisetum spicatum</i> (L.) Körn. and <i>Zea mays</i> L.) under a Low Temperature Treatment

Pearl millet (Pennisetum spicatum (L.) Körn.) and maize (Zea mays L.) are C₄ grass species grown for feeding humans and animals in Almadinah Almunawwarah, which is in the western part of Saudi Arabia. During the winter, the mean temperature, which drops to 14°C, represents a major problem for the growth of these species in this region. Therefore, the objectives of this research were to investigate the growth response and the photosynthetic performance of P. spicatum and Z. mays under a low temperature stress. The treatments involved daytime and nighttime temperatures of 14/12°C (low temperature) and 24/22°C (optimum temperature). The results indicated that low temperature significantly reduced all growth and physiological parameters, including seed germination, leaf expansion, leaf area, shoot length and root length of the two species compared to those of the control. Additionally, the low temperature significantly decreased the light-saturated assimilation rate (A_sat), quantum yield (ϕ), saturated rate of carbon dioxide uptake (A_max) and efficiency of carboxylation on both species compared to those of the control. Moreover, the values of Fv/Fm and the chlorophyll contents of both species were significantly reduced by low temperature compared to those of the control. It can be concluded that both species had little tolerance to low temperatures.     

<i>Arthrobacter agilis</i> UMCV2 accelerates growth of <i>Pinus devoniana</i>

Pinus devoniana is one of the most widely distributed species of Pinus in Mexico, and has a relevant economic and ecological importance. In this work, the effect of inoculating juvenile P. devoniana plants with the rhizobacteria Arthrobacter agilis UMCV2, and its dimethylhexadecylamine compound was studied under greenhouse conditions. Our results showed that A. agilis UMCV2 promoted growth of P. devoniana as a result of increases on height and stem diameter, fresh weight and chlorophyll concentrations. Under our experimental conditions, the bacterial dimethylhexadecylamine compound produced an increase in the concentration of chlorophyll. These data show the feasibility of using A. agilis UMCV to significantly enhance the growth rate of P. devoniana at a greenhouse scale.     

Phytosulfokine-α Promotes Root Growth by Repressing Expression of <i>Pectin Methylesterase Inhibitor</i> (<i>PMEI</i>) Genes in <i>Medicago truncatula</i>

Phytosulfokine-α (PSK-α), a sulfated pentapeptide with the sequence YIYTQ, is encoded by a small precursor gene family in Arabidopsis. PSK-α regulates multiple growth and developmental processes as a novel peptide hormone. Despite its importance, functions of PSK-α in M. truncatula growth remains unknown. In this study, we identified five genes to encode PSK-α precursors in M. truncatula. All of these precursors possess conserved PSK-α signature motif. Expression pattern analysis of these MtPSK genes revealed that each gene was expressed in a tissue-specific or ubiquitous pattern and three of them were remarkably expressed in root. Treatment of M. truncatula seedlings with synthetic PSK- α peptide significantly promoted root elongation. In addition, expression analysis of downstream genes by RNA-seq and qRT-PCR assays suggested that PSK-α signaling might regulate cell wall structure via PMEI-PME module to promote root cell growth. Taken together, our results shed light on the mechanism by which PSK-α promotes root growth in M. truncatula, providing a new resource for improvement of root growth in agriculture.     

Rapid Propagation of <i>Rhynchostylis retusa in Vitro</i>

An efficient regeneration system of Rhynchostylis retusa was established to provide technical reference for the application of tissue culture tube seedlings in production. The mixtures of callus and protocorm from aseptic germination were used as explants. The optimal media of each stage was selected for callus proliferation, protocorm occurrence and growth, rejuvenation and rooting via a single, complete combination and orthogonal experiment. The results showed that the optimal medium for callus proliferation, protocorms occurrence and growth was 1/2 Murashige and Skoog (MS) medium adding 50 g·L⁻¹ banana puree, 0.1 mg·L⁻¹ α-naphthaleneacetic acid (NAA), 1.5 mg·L⁻¹ 6-benzylaminopurine (6-BA) and 1.0 mg·L⁻¹ kinetin (KT) with 17.33 proliferation coefficient of callus and 19.63 occurrence coefficient of buds after 90 days. Then the buds occurred from protocorm were cultured on 1/2 MS medium including 100 g·L⁻¹ banana puree, 1.0 mg·L⁻¹ NAA, 2.0 mg·L⁻¹ 6-BA and 0.05 mg·L⁻¹ KT, in which the proliferation coefficient of callus was 10.32 and occurrence coefficient of buds reached 17.87. In the further subculture, the same medium was simultaneously used for callus proliferation, protocorm occurrence and bud growth. The plantlets developed roots in 1/2 MS medium containing 70 mL·L⁻¹ coconut water and 1.5 mg·L⁻¹ NAA with 100% rooting rates after 90 days. The survival rate was more than 90% after domestication and transplantation. This regeneration protocol will provide technique foundation for protecting wild resource and developing artificial cultivation.     

Cloning and Characterization of <i>EuGID1</i> in <i>Eucommia ulmoides</i> Oliver

Gibberellic acid controlled the key developmental processes of the life cycle of landing plants, and regulated the growth and development of plants. In this study, a novel gibberellin receptor gene EuGID1 was obtained from Eucommia ulmoides Oliver. The cDNA of EuGID1 was 1556 bp, and the open reading frame was 1029 bp, which encoded 343 amino acids. EuGID1 had the homology sequence with the hormone-sensitive lipase family. Amino acid sequence alignment confirmed EuGID1 protein had the highest homology with the GID1 protein of Manihot esculenta. EuGID1 was located in the nucleus and cell membrane and had expression in four plant organs. Overexpression of EuGID1 in transgenic Arabidopsis plants promoted plant elongation and increased siliques yield.     

Sexual Morph of <i>Furcasterigmium furcatum</i> (Plectosphaerellaceae) from <i>Magnolia liliifera</i> Collected in Northern Thailand

We isolated an interesting fungus from dead leaves of Magnolia liliifera collected from Chiang Mai, Thailand. The novel strain is related to Plectosphaerellaceae based on the morphology of its asexual morph and the analysis of sequence data. Phylogenetic analyses using a combined gene analysis of LSU and ITS sequence data showed that this strain is clustered in the same clade with Furcasterigmium furcatum with high statistical support. The new strains produced the asexual morph in culture which is morphologically similar to F. furcatum. Thus, we identified this strain as the sexual morph of F. furcatum. This is the first record of sexual morph for the monotypic genus Furcasterigmium and the first record of this genus on Magnolia.     

<i>Aspergillus tubingensis</i> Causes Leaf Spot of Cotton (<i>Gossypium hirsutum</i> L.) in Pakistan

Cotton (Gossypium hirsutum L.) is a key fiber crop of great commercial importance. Numerous phytopathogens decimate crop production by causing various diseases. During July-August 2018, leaf spot symptoms were recurrently observed on cotton leaves in Rahim Yar Khan, Pakistan and adjacent areas. Infected leaf samples were collected and plated on potato dextrose agar (PDA) media. Causal agent of cotton leaf spot was isolated, characterized and identified as Aspergillus tubingensis based on morphological and microscopic observations. Conclusive identification of pathogen was done on the comparative molecular analysis of CaM and β-tubulin gene sequences. BLAST analysis of both sequenced genes showed 99% similarity with A. tubingensis. Koch’s postulates were followed to confirm the pathogenicity of the isolated fungus. Healthy plants were inoculated with fungus and similar disease symptoms were observed. Fungus was re-isolated and identified to be identical to the inoculated fungus. To our knowledge, this is the first report describing the involvement of A. tubingensis in causing leaf spot disease of cotton in Pakistan and around the world.     

Effects of Nano-Cerium Oxide on Seed Germination and Seedling Growth of <i>Vitex negundo</i>

Cerium oxide nanoparticles (CeO₂NPs) are likely to have dramatic impacts on plant performances, yet the effects of CeO₂NPs on seed germination and seedling growth have not been fully explored. In this study, the seed germination and seedling growth of subshrub species Vitex negundo under different concentrations of CeO₂NPs (low-1 mg/L, medium-100 mg/L, high-500 mg/L) have been discussed. Results showed that: (1) The seed germination rate reduces by 11.25% and 2.5% under the low and medium concentrations of CeO₂NPs, respectively, but increased by 7.08% under the high concentration; (2) CeO₂NPs had significant effects on the growth traits (root length, shoot height and biomass) of seedlings, being the highest under the medium concentration and the lowest under the highest concentration; (3) The superoxide dismutase activity was the maximum (355.91 U/g), but the protein concentration was the minimum (3.85 ug/mL) under the high concentration of CeO₂NPs. Our results indicated that the effects of CeO₂NPs on seed germination and seedling growth are concentrationdependency, i.e., low and medium concentrations inhibited while high concentration promoted seed germination, however, seedling growth showed opposite responses. Therefore, appropriate CeO₂NPs concentrations are beneficial to the seed germination and seedling growth of Vitex negundo and improve the physiological performance of seedlings and enhance their adaptability to environmental adversity.     

Characterization and Candidate Gene Analysis of the Yellow-Green Leaf Mutant <i>ygl16</i> in Rice (<i>Oryza sativa</i> L.)

Leaf color mutants are ideal materials for studying many plant physiological and metabolic processes such as photosynthesis, photomorphogenesis, hormone physiology and disease resistance. In this study, the genetically stable yellow-green leaf mutant ygl16 was identified from mutated “Xinong 1B”. Compared with the wild type, the pigment concentration and photosynthetic capacity of the ygl16 decreased significantly. The ultrastructural observation showed that the distribution of thylakoid lamellae was irregular in ygl16 chloroplasts, and the grana and matrix lamellae were blurred and loose in varied degrees, and the chloroplast structure was disordered, while the osmiophilic corpuscles increased. The results of the genetic analysis and mapping showed that the phenotype of ygl16 was controlled by a pair of recessive nuclear gene. The gene located in the 56Kb interval between RM25654 and R3 on the long arm of chromosome 10. The sequencing results showed that the 121st base of the first intron of the candidate gene OsPORB/FGL changed from A to T in the interval. qRT-PCR results showed that the expression of chlorophyll synthase-related genes in the mutant decreased.     

Effects of carbohydrate substrate on the vegetative mycelial growth of an ectomycorrhizal mushroom, <Emphasis Type="Italic">Tricholoma matsutake</Emphasis>, isolated from <Emphasis Type="Italic">Quercus</Emphasis>

We studied the characteristics of the utilization of carbohydrate substrates and the production of those hydrolyzing enzymes of the Tricholoma matsutake J-1 strain isolated from hardwood (Quercus sp.). In the culture medium, 5% glucose inhibited mycelial growth. The growth inhibition rate was remarkable in the Z-1 strain from softwood (Pinus densiflora) compared with that of the J-1 strain from hardwood. α-Amylase production varied with starches from different origins in contrast to mycelial growth. The range of the effect of 0.5%–15% soluble starch on vegetative mycelial growth was also investigated. The optimal concentration for mycelial growth was 15% for the J-1 strain but 10% for the Z-1 strain. Mycelial growth of the J-1 strain was strongly inhibited in PMML medium containing Sunpeal-CP prepared from sulfite pulp softwood waste, but that of the Z-1 strain was not inhibited by Sunpeal-CP. Moreover, mycelial growth of the J-1 strain from Quercus sp. dramatically decreased with the addition of CNF-HWSF (hot water-soluble fractions from corn fiber) to the PMML and PDL medium. However, inhibition by CNF-HWSF was not shown in the Z-1 strain from P. densiflora.     

Differential Responses of <i>NHX1</i> and <i>SOS1</i> Gene Expressions to Salinity in two <i>Miscanthus sinensis</i> Anderss. Accessions with Different Salt Tolerance

The lignocellulosic crop Miscanthus spp. has been identified as a good candidate for biomass production. The responses of Miscanthus sinensis Anderss. to salinity were studied to satisfy the needs for high yields in marginal areas and to avoid competition with food production. The results indicated that the relative advantages of the tolerant accession over the sensitive one under saline conditions were associated with restricted Na⁺ accumulation in shoots. Seedlings of two accessions (salt-tolerant ‘JM0119’ and salt-sensitive ‘JM0099’) were subjected to 0 (control), 100, 200, and 300 mM NaCl stress to better understand the salt-induced biochemical responses of genes involved in Na⁺ accumulation in M. sinensis. The adaptation responses of genes encoding for Na⁺ /H⁺ antiporters, NHX1 and SOS1 to NaCl stress were examined in JM0119 and JM0099.The cDNA sequences of genes examined were highly conserved among the relatives of M. sinensis based on the sequencing on approximate 600 bp-long cDNA fragments obtained from degenerate PCR. These salt-induced variations of gene expression investigated by quantitative real-time PCR provided evidences for insights of the molecular mechanisms of salt tolerance in M. sinensis. The expression of NHX1 was up-regulated by salt stress in JM0119 shoot and root tissues. However, it was hardly affected in JM0099 shoot tissue except for a significant increase at the 100 mM salt treatment, and it was salt-suppressed in the JM0099 root tissue. In the root tissue, the expression of SOS1 was induced by the high salt treatment in JM0119 but repressed by all salt treatments in JM0099. Thus, the remarkably higher expression of NHX1 and SOS1 were associated with the resistance to Na⁺ toxicity by regulation of the Na⁺ influx, efflux, and sequestration under different salt conditions.     

Effects of <i>Piriformospora indica</i> on the Respiration of <i>Taxus chinensis</i> var. <i>mairei</i> under Water Stress

Seedlings of Taxus chinensis var. mairei were used as experimental materials to study the adaptation of Piriformospora indica to this plant under water stress. The materials were divided into two groups, namely, with or without inoculation with P. indica. Each group was subjected to four different levels of water stress. Vitality and physiological and biochemical indexes of the roots of T. chinensis var. mairei were regularly measured. Under water stress, T. chinensis var. mairei had significantly decreased root vitality; root vitality was higher in inoculated roots than in uninoculated roots. Under intense water stress, the inoculated roots had a higher soluble sugar content than the uninoculated roots. Under water stress, T. chinensis var. mairei experienced decreased activity of aerobic respiratory metabolic enzymes. The activity of anaerobic respiratory metabolic enzymes and alcohol dehydrogenase initially increased and then decreased, whereas that of lactate dehydrogenase increased. The inoculated roots had a higher activity of respiratory metabolic enzymes than the uninoculated roots. As water stress was further intensified, the roots had significantly decreased activity of aerobic respiratory metabolic enzymes and significantly increased activity of anaerobic respiratory metabolic enzymes. The activity of respiratory metabolic enzymes decreased faster in the uninoculated roots than in the inoculated roots. This study demonstrated that Piriformospora indica plays a positive role in enhancing the antihypoxic ability of T. chinensis var. mairei, thereby alleviating plant damage due to water stress.     

Comparison of conditions for mycelial growth of <Emphasis Type="Italic">Lepista sordida</Emphasis> causing fairy rings on <Emphasis Type="Italic">Zoysia matrella</Emphasis> turf to those on <Emphasis Type="Italic">Agrostis palustris</Emphasis> turf

Symptoms of fairy rings caused by Lepista sordida have been reported on Zoysiagrass (Zoysia spp.) turf maintained at fairway height (2 cm), but not on bentgrass (Agrostis spp.) maintained at putting green height (0.5 cm). The mycelia of this fungus inhabit primarily the upper 0–2 cm layer of the soil extending into the thatch. To compare conditions for the mycelial growth in Z. matrella turf to those in A. palustris turf, we examined the effects of nutrients, temperature, water potential, and pH in the field as well as in the laboratory. Greater growth of the mycelia was observed in medium that included hot water extracts from soil of the 0–1 cm zone in Z. matrella turf compared to that from A. palustris. The upper soil layer in Z. matrella turf contained more organic matter from clippings than that in A. palustris. The temperature and water potential of the 0–2 cm soil zone in Z. matrella turf were also more favorable for the mycelial growth. The soil pH values of this zone in Z. matrella turf were less favorable compared to A. palustris but within the range for accelerating mycelial growth. Part of this study was presented orally at the 46th meeting of the Mycological Society of Japan in 2002     

Identification of a Novel <i>OsCYP2</i> Allele that Was Involved in Rice Response to Low Temperature Stress

Cyclophilin (CYP) plays an important role in plant response to stress, and OsCYP2, one gene of cyclophlilin family, is involved in auxin signal transduction and stress signaling in rice. However, the mechanism that OsCYP2 is involved in rice response to low temperature is still unclear. We identified a new OsCYP2 allelic mutant, lrl3, with fewer lateral roots, and the differences in shoot height, primary root length and adventitious root length increased with the growth process compared to the wild-type plant. Auxin signaling pathway was also affected and became insensitive to gravity. The transgenic rice plants with over-expression of OsCYP2 were more tolerant to low temperature than the wild-type plants, suggesting that OsCYP2 was involved in the low temperature response in rice. In addition, OsCYP2 negatively regulated the expression of OsTPS38, a terpene synthase gene, and was dependent on the OsCDPK7-mediated pathway in response to low temperature stress. OsTPS38- overexpressed transgenic line ox-2 was more sensitive to low temperature. Therefore, OsCYP2 may negatively regulate OsTPS38 through an OsCDPK7-dependent pathway to mediate the response to low temperature in rice. These results provide a new basis for auxin signaling genes to regulate rice response to low temperature stress.