<Emphasis Type="Italic">In vitro</Emphasis> regeneration of two <Emphasis Type="Italic">Populus</Emphasis> hybrid clones. The role of pectin domains in cell processes underlying shoot organogenesis induction

An efficient plant regeneration protocol has been established for two commercial Populus hybrid clones, MC (Populus × euramericana) and UNAL (Populus × interamericana). The culture of internode segments on Murashige and Skoog (MS) medium with 0.5 μM α-naphthalene acetic acid (NAA) and 4 μM N⁶-benzyladenine for 7 weeks (2 weeks in absence of activated charcoal and 5 weeks in its presence) resulted in the highest frequency of shoot regeneration (100 % for MC and 82 % for UNAL). All regenerated shoots longer than 2 cm rooted on half-strength MS medium, independent of the addition of 0.1 μM NAA. Nevertheless, shoots developed better-formed roots in NAA-free medium, which had a positive effect on the acclimatization of plants. In order to know the cellular processes underlying in vitro shoot organogenesis, a histological study was made in UNAL internode-explants. Results revealed that in vitro culture caused swelling around the cut-off zones in all explants, but only those undergoing organogenesis formed proliferation centers under subepidermal cells, which led to formation of bud primordia. Moreover, in vivo tissues and explants with different in vitro response showed different immunolabelling patterns when they were treated with fluorescentmonoclonal antibodies directed to several pectin-polysaccharides of the cell wall. Results allow us to assign a predominant role of homogalacturonan with a low degree of methyl-esterification in the initiation of bud primordia, a role of β-1,4-D-galactan side chains of rhamnogalacturonan-I in the cellular differentiation, ra ole of α-1,5-L-arabinan side chains of rhamnogalacturonan-I and of homogalacturonan with a high degree of methyl-esterification in cell division and growth.     

The aromatic cytokinin <Emphasis Type="Italic">meta-</Emphasis>topolin promotes in vitro propagation,shoot quality and micrografting in <Emphasis Type="Italic">Corylus colurna</Emphasis> L.

The role of 4.1 or 8.2 μM meta-topolin (mT) on shoot multiplication, rooting and ex vitro acclimatization of micropropagated Corylus colurna L., a promising non-suckering rootstock for hazelnut (Corylus avellana L.), was examined in comparison to N⁶-benzyladenine (BA), the most used cytokinin in tissue culture of Corylus spp. The influence of 8.2 μM mT and BA on photosynthetic pigments content and antioxidant enzymes activity, catalase (CAT) and guaiacol peroxidase (POD), in regenerated shoots, and on the preparation of the rootstock for micrografting was also evaluated. The highest shoot multiplication was recorded on medium containing 8.2 μM mT and an overall positive effect of mT on growth and quality of micropropagated shoots was found. The highest chlorophyll a content (1.236 mg g^?1 fresh weight, FW) and chlorophyll a/b ratio (2.48), and the lowest total carotenoids content (0.292 mg g^?1 FW) and CAT activity (25.8 μmol min^?1 mg^?1 protein) were detected after 8.2 μM mT application, while no significant differences were found in chlorophyll b content and POD activity between the two cytokinins. The best rhizogenesis response (98% for 4.1 μM and 100% for 8.2 μM mT) and ex vitro acclimatization competence (higher than 78%) were exhibited from shoots multiplied on mT. Furthermore, the multiplication of rootstock on mT allowed obtaining the highest (70%) response of successful micrografting. The present findings provide the first evidence of the successful applicability of mT in C. colurna tissue culture and development of micrografted plantlets.     

Anatomy and photosystem II activity of <Emphasis Type="Italic">in vitro</Emphasis> grown <Emphasis Type="Italic">Aechmea blanchetiana</Emphasis> as affected by 1-naphthaleneacetic acid

Auxins are one of the main regulators of in vitro plant growth and development. However, the mechanisms, by which auxins, such as 1-naphthaleneacetic acid (NAA), affect in vitro root and leaf anatomy and photosystem function, remain unclear. Accordingly, the aim of the present study was to analyze the effect of different NAA concentrations on the anatomy and photosynthetic performance of in vitro-propagated Aechmea blanchetiana and to determine whether such a treatment affects micropropagated plants after acclimatization. In vitro-established A. blanchetiana plants were transferred to culture media that contained 0, 2, 4, or 6 μM NAA, and after 50 d, they were transplanted into plastic seedling trays with a commercial substrate and cultivated for 60 d in a greenhouse. The plants were evaluated after a 50-d in vitro NAA exposure (growth traits, chlorophyll α fluorescence, and root and leaf anatomy) and after 60 d of acclimatization in the greenhouse (root and leaf growth). Changes induced by NAA in root anatomy might improve uptake of minerals and sugars from the medium, thereby increasing the in vitro growth. In the leaves, the lowest chlorenchyma thickness and sclerenchyma area were observed in plants grown without NAA, and NAA exposure also improved photosystem II activity. The highest ex vitro growth rate was observed for plants that were propagated with 4 μM NAA. Therefore, the use of NAA during in vitro propagation can improve the anatomical and physiological quality of A. blanchetiana plants, as well as to improve ex vitro transfer.     

The crucial role of roots in increased cadmium-tolerance and Cd-accumulation in the pea mutant <Emphasis Type="Italic">SGECd</Emphasis><Superscript><Emphasis Type="Italic">t</Emphasis></Superscript>

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.     

Efficient callus-mediated regeneration and <Emphasis Type="Italic">in vitro</Emphasis> root tuberization in <Emphasis Type="Italic">Trichosanthes kirilowii</Emphasis> Maxim., a medicinal plant

Trichosanthes kirilowii Maxim. is a climbing herb with considerable medicinal value. In this study, efficient protocols for callus-mediated regeneration and in vitro tuberization of this plant were developed. Sterilized stem and leaf tissues were cultured on Murashige and Skoog (MS) medium with plant growth regulators (PGRs), and additives that promoted callus induction and regeneration. Both stem and leaf tissues showed the best response (100%) for callus initiation on MS medium supplemented with 4.5-μM 2,4-dichlorophenoxyacetic acid (2,4-D). Efficient shoot organogenesis was obtained by exposing the callus tissue to 4.6-μM kinetin, 2.2-μM 6-benzylaminopurine, and 2.7-μM 1-naphthylacetic acid (NAA) along with 12.6-μM copper sulfate, which yielded a shoot regeneration rate of 85.5% and 28 shoots derived from each callus. In vitro shoots were best rooted on half-strength (1/2) MS medium with 2.7-μM NAA. Tuberous roots were efficiently induced on rooting medium with 5% (w/v) sucrose under short illumination conditions (8 h photoperiod). Rooted plantlets were successfully acclimatized in pots with a >?90% survival rate. This protocol provides an effective method for callus-mediated regeneration and in vitro root tuberization.     

Accumulation and tolerance characteristics of lead in <Emphasis Type="Italic">Althaea rosea</Emphasis> Cav. and <Emphasis Type="Italic">Malva crispa</Emphasis> L.

Two ornamental plants of Althaea rosea Cav. and Malva crispa L. were exposed to various concentrations of lead (Pb) (0, 50, 100, 200 and 500 mg·kg^?1) for 70 days to evaluate the accumulating potential and the tolerance characteristics. The results showed that both plant species grown normally under Pb stress, and A. rosea had a higher tolerance than M. crispa, while M. crispa had a higher ability in Pb accumulation than A. rosea. Besides, lower Pb concentration (50 mg·kg^?1) stimulated the shoot biomass in both plant species. Pb accumulation in plants was consistent with the increase of Pb levels, and the main accumulation sites were the roots and the older leaves. In addition, the photosynthetic pigments content and chlorophyll fluorescence parameters were influenced by Pb stress. In such case, both of the plants could improve the activities of antioxidant enzymes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), and the contents of the total soluble sugar and soluble protein, which reached the highest value at Pb 100 mg·kg^?1, as well as the accumulation of the total thiols (T-SH) and non-protein thiols (NP-SH) to adapt to Pb stress. Thus, it provides the theoretical basis and possibility for ornamental plants of A. rosea and M. crispa in phytoremediation of Pb contaminated areas.     

An efficient <Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis>-mediated transformation protocol of <Emphasis Type="Italic">Withania somnifera</Emphasis>

This is the first report on Agrobacterium rhizogenes-mediated transformation of Withania somnifera for expression of a foreign gene in hairy roots. We transformed leaf and shoot tip explants using binary vector having gusA as a reporter gene and nptII as a selectable marker gene. To improve the transformation efficiency, acetosyringone (AS) was added in three stages, Agrobacterium liquid culture, Agrobacterium infection and co-culture of explants with Agrobacterium. The addition of 75 μM AS to Agrobacterium liquid culture was found to be optimum for induction of vir genes. Moreover, the gusA gene expression in hairy roots was found to be best when the leaves and shoot tips were sonicated for 10 and 20s, respectively. Based on transformation efficiency, the Agrobacterium infection for 60 and 120 min was found to be suitable for leaves and shoot tips, respectively. Amongst the various culture media tested, MS basal medium was found to be best in hairy roots. The transformation efficiency of the improved protocol was recorded 66.5 and 59.5?% in the case of leaf and shoot tip explants, respectively. When compared with other protocols the transformation efficiency of this improved protocol was found to be 2.5 fold higher for leaves and 3.7 fold more for shoot tips. Southern blot analyses confirmed 1–2 copies of the gusA transgene in the lines W1-W4, while 1–4 transgene copies were detected in the line W5 generated by the improved protocol. Thus, we have established a robust and efficient A. rhizogenes mediated expression of transgene (s) in hairy roots of W. somnifera.     

Endophytic <Emphasis Type="Italic">Alcaligenes</Emphasis> Isolated from Horticultural and Medicinal Crops Promotes Growth in Okra (<Emphasis Type="Italic">Abelmoschus</Emphasis><Emphasis Type="Italic">esculentus</Emphasis>)

The potential of endophytic bacteria to act as biofertilizers and bioprotectants has been demonstrated, and considerable progress has been made in explaining their role in plant protection. In the present study, three endophytic bacterial strains (BHU 12, BHU 16 isolated from the leaves of Abelmoschus esculentus, and BHU M7 isolated from the leaves of Andrographis paniculata) were used which displayed high sequence similarity to Alcaligenes faecalis. The biofilm formation ability of these endophytic strains in the presence of okra root exudates confirms their chemotactic ability, an initial step for successful endophytic colonization. Further, reinoculation of spontaneous rifampicin-tagged mutants into okra seedlings revealed a CFU count above 10⁵ cells g^?1 of all three endophytic strains in root samples during the first 15 days of plant growth. The CFU count increased up to 10¹³ by 30 days of plant growth, followed by a gradual decline to approximately 10¹⁰ cells g^?1 at 45 days of plant growth. Systemic endophytic colonization was further supported by 2, 3, 5-triphenyl tetrazolium chloride staining and fluorescence imaging of ds-RED expressing conjugants of the endophytic strains. The strains were further assessed for their plausible in vivo and in vitro plant growth-promoting and antagonistic abilities. Our results demonstrated that the endophytic strains BHU 12, BHU 16, and BHU M7 augmented plant biomass by greater than 40 %. Root and shoot lengths of okra plants when primed by BHU 12, BHU 16, and BHU M7 increased up to 34 and 14.5 %, respectively. The endophytic isolates also exhibited significant in vitro antagonistic potential against the collar rot pathogen Sclerotium rolfsii. In summary, our results demonstrate excellent potential of the three endophytic bacterial strains as biofertilizers and biocontrol agents, indicating the possibility for use in sustainable agriculture.     

Heterologous expression of a novel <Emphasis Type="Italic">Poa pratensis</Emphasis> gibberellin 2-oxidase gene, <Emphasis Type="Italic">PpGA2ox</Emphasis>, caused dwarfism,late flowering,and increased chlorophyll accumulation in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Gibberellin 2-oxidases (GA2oxs) irreversibly convert bioactive gibberellins (GAs) and their immediate precursors into inactive GAs via 2-β hydroxylation and so regulate gibberellin content in plants. However, to the best of our knowledge, little has been known about the GA2oxs and its function in cool season turfgrass Poa pratensis. In this study, rapid amplification of cDNA end (RACE) was employed to isolate PpGA2ox from P. pratensis. The open reading frame of PpGA2ox was 1 047 bp in length, corresponding to 348 amino acids. PpGA2ox was localized in both nucleus and cytoplasm. The expression of PpGA2ox could be up-regulated by 10 μM gibberellic acid, 5 μM methyl jasmonate, or 10 μM indole-3-acetic acid. In addition, its native promoter could drive GUS expression in both leaf apex and shoot apical region. Moreover, overexpression of PpGA2ox in Arabidopsis led to GA-deficiency leading to dwarf phenotype, delayed flowering time, and increased chlorophyll content. Our study suggests that PpGA2ox could be a candidate gene for breeding new cultivars of P. pratensis.     

The <Emphasis Type="Italic">APX4</Emphasis> locus regulates seed vigor and seedling growth in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

The amino acid sequence of APX4 is similar to other ascorbate peroxidases (APXs), a group of proteins that protect plants from oxidative damage by transferring electrons from ascorbate to detoxify peroxides. In this study, we characterized two apx4 mutant alleles. Translational fusions with GFP indicated APX4 localizes to chloroplasts. Both apx4 mutant alleles formed chlorotic cotyledons with significantly reduced chlorophyll a, chlorophyll b and lutein. Given the homology of APX to ROS-scavenging proteins, this result is consistent with APX4 protecting seedling photosystems from oxidation. The growth of apx4 seedlings was stunted early in seedling development. In addition, APX4 altered seed quality by affecting seed coat formation. While apx4 seed development appeared normal, the seed coat was darker and more permeable than the wild type. In addition, accelerated aging tests showed that apx4 seeds were more sensitive to environmental stress than the wild-type seeds. If APX4 affects seed pigment biosynthesis or reduction, the seed coat color and permeability phenotypes are explained. apx4 mutants had cotyledon chlorosis, increased H₂O₂ accumulation, and reduced soluble APX activity in seedlings. These results indicate that APX4 is involved in the ROS-scavenging process in chloroplasts.     

Mycorrhizal synthesis between <Emphasis Type="Italic">Lactarius deliciosus</Emphasis> and <Emphasis Type="Italic">Arbutus unedo</Emphasis> L.

Arbutoid mycorrhizae were synthesized in vitro between Arbutus unedo L. and two isolates of Lactarius deliciosus. The fungal isolates were obtained from sporocarps collected under Pinus sylvestris and in a mixed forest stand of Quercus suber and Pinus pinea. Synthesis tubes filled with a mixture of sterilized peat, vermiculite, and perlite imbibed with nutrient solution were used. Two inoculation methods using solid and liquid media were tested. Shoots from an adult selected clone of A. unedo were used after in vitro rooting by auxin dipping. After 3 months of shoots transfer to the substrate, the root systems were examined for arbutoid mycorrhizae formation and later on ex vitro conditions, 9 months after acclimatization. The inoculum treatment with liquid medium improved the mycorrhizal development for both isolates, in vitro. Sterilized substrate for plant acclimatization increased the mycorrhizal development. The arbutoid mycorrhizae were observed in vitro as well as 9 months after acclimatization. Standard arbutoid mycorrhiza features were observed: pale yellow mantle, typical cruciform appearance, Hartig net (HN), and intracellular hyphal complexes, both confined to the epidermis. L. deliciosus mycorrhizae synthetized in vitro persisted 9 months after plant acclimatization. Morphological observations were confirmed by molecular techniques.     

Effect of over-expression of <Emphasis Type="Italic">Linum usitatissimum</Emphasis> PINORESINOL LARICIRESINOL REDUCTASE (<Emphasis Type="Italic">LuPLR</Emphasis>) gene in transgenic <Emphasis Type="Italic">Phyllanthus amarus</Emphasis>

Shoot tip explants of Phyllanthus amarus were cocultivated with Agrobacterium tumefaciens strain LBA 4404 carrying plasmid pCAMBIA 2301 harbouring genes coding for betaglucuronidase (gus), kanamycin (kan), and neomycin phosphotransferase II (nptII) along with a gene coding for Linum usitatissimum PINORESINOL LARICIRESINOL REDUCTASE (Lu-PLR). Transformed shoot tip explants were maintained in a Murashige and Skoog (MS) medium containing TDZ 1.54 mg l^?1, kan 50 mg l^?1 and cephotaxime 62.5 mg l^?1. The optimum medium for regeneration of multiple shoots was MS supplemented with TDZ 1.54 mg l^?1, kan 50 mg l^?1. Efficient and effective rooting of plantlets was achieved by culturing the in vitro regenerated shoots on liquid ½ MS medium containing 0.7 mg l^?1 indole 3-butyric acid (IBA) and 5 mg l^?1 kan. Rooted plants were acclimatized in the mixtures of vermiculite and soil. The transformation of kan-resistant plantlets regenerated from shoot-tip explants was confirmed by GUS and polymerase chain reaction (PCR) analysis. Southern blot and reverse transcribed PCR (RT-PCR) analysis confirmed successful integration and expression of Lu-PLR gene. Quantitative analysis of phyllanthin performed on transgenic and wild plants using high-performance liquid chromatography (HPLC) revealed that transgenic lines contained higher phyllanthin content (0.3–0.81% w/w) than wild plants (0.09% w/w). The highest yield of phyllanthin was detected in transgenic lines was up to 1.16, 1.22 and 1.23 folds higher than that of wild plant. This report highlights the transgenic approach to enhance the contents of phyllanthin and hypophyllanthin.     

Effect of microalgae hydrolysate foliar application (<Emphasis Type="Italic">Arthrospira platensis</Emphasis> and <Emphasis Type="Italic">Scenedesmus</Emphasis> sp.) on <Emphasis Type="Italic">Petunia x hybrida</Emphasis> growth

In horticultural practice accelerated plant development and particularly earlier flowering, has been reported with microalgae applications. Therefore, the objective of this work was to study the effects of foliar spraying with Scenedesmus sp. and Arthrospira platensis hydrolysates on Petunia x hybrida plant development and leaf nutrient status. Three treatments were tested: T1 (foliar application with water, the control), T2 (foliar application with Arthrospira), and T3 (foliar application with Scenedesmus). Foliar spraying was applied five times (0, 14, 28, 35, and 42 days after transplanting). The concentration of both microalgae was 10 g L^?1. At the end of the trial biometric parameters and nutrient concentration in photosynthetic organs (the leaves) were measured. The results of this assay show that foliar application of Scenedesmus accelerated plant development in terms of higher rates of root growth, leaf and shoot development, and earliness of flowering. Arthrospira enhanced the root dry matter, the number of flowers per plant, and the water content. Nevertheless, a reduction was found in the conductive tissue (stem + petiole) dry weight with Arthrospira compared with Scenedesmus and the control. The results also show that microalgae hydrolysate supply can improve the plant nutrient status. Based on these results, it is advisable to use Scenedesmus hydrolysates in foliar applications to increase the blooming of Petunia x hybrida.     

<Emphasis Type="Italic">In vitro</Emphasis> Blastogenesis inhibited by <Emphasis Type="Italic">Erwinia carotovora</Emphasis><Emphasis Type="SmallCaps">L</Emphasis>-Asparaginase

Escherichia coliL-asparaginase, an antileukaemic agent in man¹, inhibits in vitro mitogen or antigen-induced blastogenesis in man^2,3 and in animals (M. Bennett, E. G. Mayhew and T. Han, unpublished data) and suppresses bone-marrow derived antibody precursor cells in the mouse⁴. We now report that another L-asparaginase preparation—from Erwinia carotovora—also possesses antileukaemic activity^5,6 and has a more pronounced immunosuppressive effect on in vitro blastogenesis than the E. coli enzyme.     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration of <Emphasis Type="Italic">Melothria maderaspatana</Emphasis> via indirect organogenesis

An effective protocol was developed for in vitro regeneration of the Melothria maderaspatana via indirect organogenesis in liquid and solid culture systems. Organogenesis was achieved from liquid culture calluses derived from leaf and petiole explants of mature plants. Organogenic calluses (98.2?±?0.36 and 94.8?±?0.71%) were induced from both leaf and petiole explants on Murashige and Skoog (MS) liquid medium containing 6.0 µM 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 µM thidiazuron (TDZ); and 6.0 µM 2,4-D and 1.0 µM benzyladenine (BA) combinations, respectively. Adventitious shoot regeneration (68.2?±?0.06 shoots per explant) was achieved on MS medium supplemented with 2.0 µM BA, 4.0 µM TDZ, 10% v/v coconut water and 0.06 mM glutamine from leaf-derived calluses. Petiole-derived calluses produced adventitious shoots (45.4?±?0.09 shoots per explant) on MS medium fortified with 2.0 µM BA, 4.0 µM TDZ, 10% v/v coconut water, and 0.08 mM glutamine. Elongation of shoots occurred in MS medium with 2.0 µM gibberellic acid (GA₃). Regenerated shoots (2–3 cm in length) rooted (74.2?±?0.38%) and hardened (85?±?1.24%) when they were transferred to 1/2-MS medium supplemented with 3.0 µM indole-3-butyric acid (IBA) followed by garden soil, vermiculate, and sand (2:1:1 ratio) mixture. The elongated shoots (4–5 cm in length) were exposed simultaneously for rooting as well as hardening (100%) in moistened [(1/8-MS basal salt solution with 5 µM IBA and 100 mg l^?1 Bavistin® (BVN)] garden soil, vermiculate, and sand (2:1:1 ratio) mixture. Subsequently, the plants were successfully established in the field. The survival percentage differed with seasonal variations.     

Overexpression of <Emphasis Type="Italic">MuHSP70</Emphasis> gene from <Emphasis Type="Italic">Macrotyloma uniflorum</Emphasis> confers multiple abiotic stress tolerance in transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

A 70-KD heat shock protein (HSP70) is one of the most conserved chaperones. It is involved in de novo protein folding and prevents the aggregation of unfolded proteins under lethal environmental factors. The purpose of this study is to characterise a MuHSP70 from horsegram (Macrotyloma uniflorum) and elucidating its role in stress tolerance of plants. A MuHSP70 was cloned and characterised from a natural drought stress tolerant HPK4 variety of horsegram (M. uniflorum). For functional characterization, MuHSP70 was overexpressed in transgenic Arabidopsis. Overexpression of MuHSP70 was found to provide tolerance to the transgenic Arabidopsis against various stresses such as heat, cold, drought, salinity and oxidative stress. MuHSP70 transgenics were observed to maintain the shoot biomass, root length, relative water content, and chlorophyll content during exposure to multi-stresses relative to non-transgenic control. Transgenic lines have further shown the reduced levels of MDA, H₂O₂, and proteolytic activity. Together, these findings suggest that overexpression of MuHSP70 plays an important role in improving abiotic stress tolerance and could be a crucial candidate gene for exploration in crop improvement program.