Exogenous Naphthalene Acetic Acid Research Articles

The combined analysis of transcriptome and phytohormone provides new insights into signaling mechanism for lateral root formation of tea plant (Camellia sinensis)

The growth and development of lateral roots (LRs) determine the nutrient absorption and environmental adaptability of tea plant, playing a crucial role in the economic efficiency of tea plantations. However, the molecular mechanisms underlying the formation of LRs in tea plant remain unreported. In this study, we established a LRs induction system in tea plants by exogenously adding N-1-naphthylphthalamic acid (NPA) and naphthaleneacetic acid (NAA). The molecular mechanisms of LRs formation were analyzed through transcriptomics and endogenous hormone measurements. Results showed that NAA treatment could counteract the inhibitory effect of NPA on LRs formation and promote the generation of LRs in tea plant. The addition of exogenous NAA reduced the levels of auxin and zeatin in the root tips while increasing the content of abscisic acid (ABA). Transcriptomic analysis at four time points (2, 6, 12, and 24 h) after NAA vs. MOCK treatment revealed 78 different expression genes (DEGs) associated with plant hormone signaling pathways. Among these, the auxin signaling pathway was the most significant in responding to the LRs formation in tea plant. Weighted Gene Co-Expression Network Analysis (WGCNA) identified the Mitogen-Activated Protein Kinases (MAPK) signaling pathway as responsive to NAA treatment, participating in the formation of LRs in tea plant. This study provides potential signaling pathways for the investigation of LRs formation in tea plant and identifies candidate genes for further research into tea plant root system architecture (RSA).

Effects of exogenous auxin on yield in foxtail millet (Setaria italica L.) when applied at the grain-filling stage.

Foxtail millet (Setaria italica L.) is of high nutritious value, which is an important crop in arid and semi-arid regions. The objective of this experiment was to explore the effects of the synthetic auxin naphthalene acetic acid (NAA) on the physiological processes of foxtail millet, and to provide a theoretical basis and technical approaches for its efficient use in millet cultivation. Two foxtail millet varieties ('Jingu 21' and 'Zhangzagu 5') were treated with six concentrations of NAA from 0-144 mg L-1 at the grain-filling stage in field experiments. The photosynthetic pigment contents, gas exchange parameters, chlorophyll fluorescence parameters, and grain yield were measured in foxtail millet. The results showed that low concentrations of NAA (18-36 mg L-1) increased the contents of photosynthetic pigments, and increased the activities of antioxidant enzymes, the photosynthetic rate, and the activity of photosystem system II (PS II). At higher NAA concentrations, the facilitation effect of the treatments diminished, showing a clear concentration effect. In this study, yield was significantly and positively correlated with PS II effective quantum yield (Y(II)) and the PSII electron transport rate (ETR), and the net photosynthetic rate (Pn) was significantly and positively correlated with chlorophyll content, stomatal conductance (Gs), Y(II), and ETR. These results also indicated that exogenous NAA application promotes the production of ATP and NADPH by increasing the efficiency of electron transfer within the photosystems and also improved photochemical utilization, which facilitates the fixation and reduction of carbon, ultimately leading to an increase in Pn and increasing grain yield in foxtail millet.

BSISTER transcription factors directly binds to the promoter of IAA19 and IAA29 genes to up-regulate gene expression and promote the root development

Roots play an important role in the growth and development of plants and auxin participates in regulating plant root development. Some studies have shown that BS (BSISTER) gene (the closest gene of class B gene) is involved in plant root development, but whether BS regulates root development via auxin signaling still not clear. To explore VviBS1 and VviBS2 roles in root development, VviBS1 and VviBS2 were overexpressedin Arabidopsis tt16 mutant and we found that they could restore the phenotype of shorter PR (primary roots) and high density of LR (lateral root) of tt16 compared with the wild type Ws Arabidopsis seedlings. However, the addition of exogenous NAA (naphthalene acetic acid) could not significantly promote the PR length of tt16 Arabidopsis, and the auxin signal transduction of tt16 may be blocked. The expression levels of auxin signal transduction pathway genes in Ws, tt16, p35s:VviBS1 in tt16 and p35s:VviBS2 in tt16 seedlings were detected. It was found that the expression of AtARF2, AtARF12, AtARF14, AtARF15, AtARF20, AtGH3, AtGH3-2 and AtSAUR51 genes in tt16 seedlings was higher than that in Ws, while the expression of AtIAA19 and AtIAA29 in Ws seedlings was higher than that of tt16. More importantly, BS may up regulate AtIAA19 and AtIAA29 expression directly by binding to their promoter. In addition, VviBS1 and VviBS2 also affect seed germination and may regulate leaf yellowing by regulating ethylene synthase. Therefore, our findings reveal a molecular mechanism that BS may modulate root system development via Aux/IAA-based auxin signaling, and provide insight into the BS function in regulation of leaf yellowing.

Optimization of rhizogenesis for in vitro shoot culture of Pinusmassoniana Lamb.

The rooting capacity of Pinusmassoniana is poor, especially for mature trees, and has prevented the development of clonal forestry for P.massoniana. In this study, we varied explant types, subculture times and exogenous hormones for plantlet regeneration and assessed shoots for rooting rate and root number for P.massoniana. Following five repetitive grafts, new shoots from grafts used as explant sources were rejuvenated as observed from juvenile shoot morphology and anatomy, leading to greatly enhanced plant regeneration in comparison to that of mature materials from 26-year-old P.massoniana trees. The rooting capacity of subcultured shoots increased with successive subcultures, reaching a peak at 20 subcultures with 35–40 days per subculture. However, rooting performance was significantly reduced after 30 subcultures. The addition of naphthaleneacetic acid (NAA) plus indoleacetic acid in the medium improved the root number, but the combination of exogenous NAA with paclobutrazol (PBZ) increased rooting rate and root number. We thus greatly improved the rooting capacity of mature P.massoniana trees by optimizing explant types (rejuvenated), subculture times (20 subcultures, 35–40 days per subculture) and addition of NAA + PBZ to the rooting medium. The conditions can be used for efficient plantlet regeneration of P.massoniana.

Effects of benzyladenine and α-naphthaleneacetic acid on the early growth phase of Ananas comosus (L.) Merr.

In this study, benzyladenine (BA) and α- naphthaleneacetic acid (NAA) are used to study the growth of pineapple fruit (Ananas comosus (L.) Merr.) in the early growth phase. Pineapple fruits are sprayed with BA or NAA at different concentrations (1, 5, 10, 20, 40 and 60 mg.L-1) at both 0 and 3 days after flowering (DAF, 50 % dried flowers). Fruits are sampled every 15 days from 0 to 75 days to survey to weight, size and qualities of pineaple fruit. Besides, fruits (which are sprayed with BA or NAA at concentration 20 mg.L-1) are sampled at 15 days for the cell size observation. The results showed that the treatments with three highest concentration of BA or NAA (20, 40 và 60 mg.L-1) significantly increased fruit weights and fruit sizes. Exogenous BA or NAA at the concentration 20 mg.L-1 increased the fruit weights by increasing the number of flesh cells without negative effects on fruit qualities.

Effects of benzyladenine and α-naphthaleneacetic acid on the early growth phase of Ananas comosus (L.) Merr.

In this study, benzyladenine (BA) and α- naphthaleneacetic acid (NAA) are used to study the growth of pineapple fruit (Ananas comosus (L.) Merr.) in the early growth phase. Pineapple fruits are sprayed with BA or NAA at different concentrations (1, 5, 10, 20, 40 and 60 mg.L-1) at both 0 and 3 days after flowering (DAF, 50 % dried flowers). Fruits are sampled every 15 days from 0 to 75 days to survey to weight, size and qualities of pineaple fruit. Besides, fruits (which are sprayed with BA or NAA at concentration 20 mg.L-1) are sampled at 15 days for the cell size observation. The results showed that the treatments with three highest concentration of BA or NAA (20, 40 và 60 mg.L-1) significantly increased fruit weights and fruit sizes. Exogenous BA or NAA at the concentration 20 mg.L-1 increased the fruit weights by increasing the number of flesh cells without negative effects on fruit qualities.

The effects of exogenous hormones on rooting process and the activities of key enzymes of Malus hupehensis stem cuttings.

Malus hupehensis is an excellent Malus rootstock species, known for its strong adverse-resistance and apomixes. In the present study, stem cuttings of M. hupehensis were treated with three types of exogenous hormones, including indole acetic acid (IAA), naphthalene acetic acid (NAA), or green growth regulator (GGR). The effects and mechanisms of exogenous hormone treatment and antioxidant enzyme activity on adventitious root formation were investigated. The results showed that the apparent morphology of the adventitious root had four stages, including root pre-emergence stage (S0), early stage of root formation (S1), massive root formation stage (S2), and later stage of root formation (S3). The suitable concentrations of the three exogenous hormones, IAA, NAA and GGR, were 100 mg·L-1, 300 mg·L-1, and 300 mg·L-1, respectively. They shortened the rooting time by 25–47.4% and increased the rooting percentages of cuttings by 0.9–1.3 times, compared with that in the control. The dispersion in S0 stage was 3.6 times of that in the S1 stage after exogenous hormone application. The earlier the third critical point (P3) appeared, the shorter the rooting time and the greater the rooting percentage of the cuttings. During rhizogenesis, the activities of three antioxidant enzymes (POD, SOD, and PPO) showed an A-shaped trend. However, peak values of enzyme activity appeared at different points, which were 9 d before the P3, P3, and the fourth critical point (P4), respectively. Exogenous hormone treatment reduced the time to reach the peak value by 18 days, although the peak values of the enzymatic activities did not significantly changed. Our results suggested that exogenous hormone treatment mainly acted during the root pre-emergence stage, accelerated the synthesis of antioxidant enzymes, reduced the rooting time, and consequently promoted root formation. The three kinds of antioxidant enzymes acted on different stages of rooting.

Effect of growth hormones on some antioxidant parameters and gene expression in tomato

Bioregulators have a great effect on vital processes of plant growth and development. Known plant bioregulators include Naphthalene acetic acid (NAA), Indole-3-butyric acid (IBA) and Indole-3-acetic acid (IAA). Natural or synthetic plant bioregulators are organic compounds that affect the physiological processes in the plant, either to control some of these processes or to modify them. For example these bioregulators can affect the nature of the process, either by accelerating or decelerating plant growth, rates of maturation and also by altering the behavior of the plants or their products. Also, enhancement of important nutrients in human diet could be achieved by bioregulators. This study uses the model crop plant Tomato (Lycopersicon esculentum). Tomato is affected by a group of bioregulators, this group contains compounds which are powerful antioxidants in vitro. The current study aims to find out the effect of some plant bioregulators (IAA, IBA and NAA) on tomato growth, total protein content and enzyme activities of ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT). This study also investigates the effect of the above mentioned bioregulators on the level of RNA expression for SOD, CAT and TPX1 genes. The analytical quantification of target gene expression showed the induced effect of NAA on SOD expression and reducing effect of the other bioregulators (IAA and IBA) on CAT and TPX1 expression. However, at the protein level, we found that IBA and IAA caused a minor effect on total protein content while a significant effect was recorded on the total protein level using NAA. Upon measuring the enzyme activity of ascorbate peroxidase and catalase, we found that both the exogenous NAA and IBA stimulated ascorbate peroxidase activity in tomato while there was no considerable difference detected in IAA treated plants. Also, there was no considerable difference detected in catalase activity of all bioregulator-treated plants compared with the control.

Molecular and Physiological Changes in Maize (Zea mays) Induced by Exogenous NAA, ABA and MeJa during Cold Stress

Different concentrations of abscisic acid (ABA), naphthalene acetic acid (NAA) and methyl jasmonate (MeJa) were applied to maize (Zea mays) plants exposed to cold stress. ABA enhanced plant resistance against the damaging effects of freezing. ABA-treated plants produced some specific proteins when exposed to cold. Prominent changes were observed in the size and number of stomata with the application of ABA during cold stress. MeJa inhibited root growth, but increased root dry weight during cold acclimation. The chlorophyll content was lower at 100 µg ml-1 NAA and 50 µg ml-1 MeJa and higher in the residual applications when compared with that in the control plants. Carotenoid levels increased in all NAA and some ABA treatments, decreased however in MeJa treatment. Exogenous MeJa treatments increased endogenous trans-zeatin (t-Z) and indole-3-acetic acide (IAA) in contrast decreased ABA levels. Exogenous NAA also increased endogenous IAA, ABA and zeatin riboside (ZR) levels, while exogenous ABA decreased endogenous IAA and ZR levels.

Naphthaleneacetic acid suppresses peroxidase activity during the induction of adventitious roots in soybean hypocotyls

The synthetic auxin naphthaleneacetic acid (NAA) promoted rooting in soybean (Glycine max) hypocotyls. The activity of anionic peroxidases (PODs, pI 3.5, pI 3.7 and pI 4.4) and cationic PODs (pI 8.3, pI 9.1 and pI 9.4) was significantly inhibited by exogenous NAA during the induction of adventitious roots. In addition, the reduction in POD activity (pI 4.4, pI 8.3 and pI 9.4) correlated with a reduction in corresponding transcription activity. POD patterns and transcription in NAA-treated hypocotyls demonstrated the specific effect of NAA on POD isozymes, indicating that NAA suppresses POD gene expression during the induction of adventitious root. The decline of POD activity in NAA-treated hypocotyls was accompanied by a decrease in lignin content. We suggest that both anionic and cationic PODs might be involved in lignin synthesis in soybean hypocotyls.

A comparison of the effects of auxin on cluster root initiation and development in Grevillea robusta Cunn. ex R. Br. (Proteaceae) and in the genus Lupinus (Leguminosae).

The effect of NAA (naphthaleneacetic acid) on the development of cluster roots in members of the Proteaceae and Leguminosae was investigated. The exogenous addition of NAA led to initiation of cluster roots in phosphate conditions normally inhibitory for their development, but initiation took place within the limits of the cluster pattern under −P conditions. There was no change in spacing within the cluster root nor between cluster roots in Grevillea robusta Cunn. ex R. Br. or in rootlet length or cluster root length. In Lupinus albus L., change in rootlet length and cluster root length was noted at 10-10 and 1012 M NAA. In L. albus, the length of time that roots were exposed to NAA does not appear to be important, with similar levels of cluster root initiation after 48 h and 7 days. Cluster root production in G. robusta differed from that in L. albus in terms of the concentration of NAA needed to induce initiation, and in the effects of extremely low levels of NAA on rootlet numbers and lengths. L. arboreus L. does not produce cluster roots under −P conditions. Furthermore, neither L. arboreus L., L. angustifolius L., L. luteus L. nor L. mutabilis L. were induced to produce cluster roots under −P conditions, nor under +P conditions in the presence of exogenous NAA. Thus, exogenous NAA only leads to the induction of cluster roots, at levels of P normally inhibitive of their development, in species of Lupinus that produce them under −P conditions. Auxin-induced cluster roots develop within the same constraints as those developing under −P conditions. NAA does not induce cluster roots in species of Lupinus that do not produce them under −P conditions.

Cortical tissue-specific accumulation of the root-specific ns-LTP transcripts in the bean (Phaseolus vulgaris) seedlings.

The characterization of a cDNA clone encoding non-specific lipid transfer protein (PvLTP, formerly named PVR3) in the roots of bean seedlings has been previously reported. In this study, we examined the temporal and spatial accumulation of PvLTP mRNA and the effect of the auxin naphthaleneacetic acid (NAA) on the accumulation of PvLTP mRNA during root development. In situ hybridization showed that accumulation of PvLTP mRNA is highly tissue-specific. Accumulation was detected in the cortical tissue, but not in other tissues of root, including the quiescent center and root cap. Within the cortical tissue, accumulation of PvLTP mRNA was developmentally regulated; accumulation of PvLTP mRNA was high in the cortical tissue of the proximal and ground meristem and declined as cortical tissue developed further. Since the appropriate distribution of auxin is an important factor responsible for the maintenance of root meristem organization. We examined effect of auxin on the accumulation of PvLTP mRNA in relation to the development of cortical tissue. In bean seedlings grown on medium supplemented with 5 microM NAA, morphological alternations, including radial root expansion and abnormal tissue organization in the root apical meristem, were observed. Only faint accumulation signals of PvLTP mRNA were observed in the cortical tissue of proximal meristem region, indicating that cortical tissue development was repressed by exogenous NAA. However, our results suggest that the change in accumulation of PvLTP mRNA is not direct regulatory effect but reflective effect of altered development of cortical tissue that was induced by exogenous NAA. The temporal and spatial accumulation of PvLTP mRNA indicates that PvLTP is a useful marker for the development of cortical tissue in the root tip in bean seedlings.