Rubisco Activase Gene Research Articles

Heat stress induced cytosine methylation in the coding region of Rubisco activase (Rca) reveals its genotype-specific expression in contrasting wheat genotypes

Rising environmental temperature has become a major concern in global wheat production since it has critical effects on plant growth,development and yield. Elevated temperatures have become. Further understanding of the processes behind the development of heattolerance is necessary for significant agricultural crops. Cytosine methylation in DNA plays an essential function in epigenetic regulation of gene expression at various developmental stages and environmental stress in plants. In this study, we report the comparative analysis of cytosine methylation in the coding region of the Rubisco activase (Rca) gene in heat tolerant (RAJ3765) and heat susceptible (HUW510)genotypes of wheat in four growth stages under control and heat-stressed conditions in CG, CHG and CGG contexts. We found that the overall 5-mC increased due to heat stress in HUW510 during tillering (25%), boot stage (25%), heading (48%) and anthesis (50%) as compared to RAJ3765 during tillering (21%), boot stage (4%), heading (4%) and anthesis (11%). Additionally, gene expression profiling by using qPCR at the different plant growth stages also showed the decline in the gene expression in the leaf samples in both the genotypes due to heat stress, with a minimum in the susceptible genotype at the anthesis stage. The study will increase the knowledge on the molecular regulation of photosynthetic pathways by cytosine methylation which would assist in selection and manipulation of heat tolerance in wheat.

Effects of blue and red LED lights on rubisco activase gene expression, CO2 fixation efficiency and plant morphology of Gerbera jamesonii

Light quality is known to affects numerous plants’ physiological and metabolic processes during development period, including photosynthesis and morphogenesis. Light properties such as light wavelength has been optimized for several cultivated crops. In this study, the effects of LED light wavelengths blue and red on both photosynthetic performance and morphology of Gerbera jamesonii plantlets was investigated. The results showed the photosynthesis efficiency via the photo-pigment system and mediated regulation of rubisco activase encoding gene (RCA) mechanism was significantly enhanced by blue light. The expression of RCA was approximatly 2.7 times higher than those under red light. In contrast, chlorophyll contents, CO2 assimilation, total carbohydrate and RCA expression was reduced under red wavelength. However, both single-wavelengths caused a dramatically negative impact on G. jamesonii. Total chlorophyll/carotenoid value or higher carotenoid contents was lower under blue light; fragile petioles and drawrfism morphology was occurred under red and blue LED, respectively. The combination of blue and red light in the lighting spectrum significantly improved the limitations of single-wavelength. The supplement of blue light under red light background (at blue LED and red LED ratio = 1:4) improved plant photosynthesis while maintained the normal morphology of plants, although the expression of RCA and net photosynthesis of plants in BR LED was lower than in the control. Our results obviously provide the scientific evidences for requirement of LED light in micropropagation or canopy culture of G. jamesonii.

Cloning and Characterization of the RubisCO Activase Gene from Pinus massoniana

Cloning and Characterization of the RubisCO Activase Gene from Pinus massoniana

A long transcript mutant of the rubisco activase gene RCA upregulated by the transcription factor Ghd2 enhances drought tolerance in rice.

The transcription factor Ghd2 increases rice yield potential under normal conditions and accelerates leaf senescence under drought stress. However, its mechanism on the regulation of leaf senescence under drought stress remains unclear. In the present study, to unveil the mechanism, one target of Ghd2, the Rubisco activase gene RCA, was identified through the combined analysis of Ghd2-CRISPR transcriptome data and Ghd2-overexpression microarray data. Ghd2 binds to the 'CACA' motif in the RCA promoter by its CCT domain and upregulates RCA expression. RCA has alternative transcripts, RCAS and RCAL, which are predominantly expressed under normal conditions and drought stress, respectively. Similar to Ghd2-overexpressing plants, RCAL-overexpressing plants were more sensitive to drought stress than the wild-type. However, the plants overexpressing RCAS showed a weak drought-sensitive phenotype. Moreover, RCAL knockdown and knockout plants did not show yield loss under normal conditions, but exhibited enhanced drought tolerance and delayed leaf senescence. The chlorophyll content, the free amino acid content and the expression of senescence-related genes in the RCAL mutant were lower than those in the wild-type plants under drought stress. In summary, Ghd2 induces leaf senescence by upregulating RCAL expression under drought stress, and the RCAL mutant has important values in breeding drought-tolerant varieties.

Response of Chinese sea buckthorn clonal growth and photosynthetic physiological mechanisms toward a soil moisture gradient

Studies have reported on the regulation of clonal growth in Chinese sea buckthorn in response to environmental resource availability, but these studies have been limited to external mechanisms. In this report, we controlled irrigation to generate a soil moisture gradient in order to examine the photosynthetic physiological mechanisms regulating clonal growth in this species. The results indicated that as irrigation intensity increased, the soil water content increased vertically and tissue water content first increased and then decreased. Furthermore, Rubisco activase (RCA) and Mg-chelatase H subunit (CHLH) gene expression levels, photosynthetic capacity (net photosynthetic rate, transpiration rate, chlorophyll content, and stomatal conductance), and clonal growth (ramet growth, clonal proliferation, clonal propagation) all showed a quadratic parabolic change (i.e., first increasing and then decreasing). In addition, gene expression levels and tissue water content, photosynthetic capacity and gene expression levels, and clonal growth and photosynthetic capacity were all significantly positively correlated. When irrigation intensity (soil water content) is exceedingly low or high, the tissue water content is also low, RCA and CHLH gene expression levels are low, photosynthetic capacity is weak, clonal growth ability is inhibited, and clonal growth layout tends toward the “guerrilla type.” This type manifests as fewer and smaller clonal daughter ramets that are sparsely distributed with reduced clonal organ extension ability and branching intensity. When irrigation intensity (soil water content) is moderate, the tissue water content, gene expression levels, and photosynthetic capacity is high, clonal growth ability is completely uninhibited, and the clonal growth layout tends toward the “aggregated type.” This type is associated with numerous large clonal daughter ramets that are densely distributed with high clonal organ extension ability and branching intensity. Therefore, as irrigation intensity continuously changes from inordinately low to moderate to exceedingly high, Chinese sea buckthorn regulates clonal growth by photosynthetic capacity through photosynthetic gene expression. This results in a clonal growth layout continuum of “guerrilla-aggregated-guerrilla” that depends on irrigation intensity.

Leaf antioxidant machinery stimulation by Meloidogyne javanica infestation: A case study on Cucumis melo seedlings

Following nematode infestation, leaf-localized responses are vital not only as early infection signs but also as an indication of actions required to preserve crop productivity. In this context, the leaf-level physiological responses of cantaloupe seedlings were evaluated after 40 consecutive days of cultivation under different Meloidogyne javanica juveniles (J2s) inoculation regimes (0, 100, and 850 J2s plant−1). Leaf growth parameters and photosynthetic pigments (chlorophyll, carotenoids) content were not affected by J2s infestation, while foliar Potassium concentration significantly declined. The RuBIsCo activase gene expression was negatively associated with the J2s inoculation level. Total flavonoids, total phenolics, lipid peroxidation indexes, phenylalanine ammonia-lyase activity, as well as, ascorbate peroxidase gene transcription, were higher in the inoculated plants (regardless of the J2s inoculant level). Taken together, present data indicate that J2s infestation impacts primarily the Potassium levels in leaves. Additionally, a substantial stimulation of the plant antioxidant machinery (independent of the nematode infestation intensity) is triggered. Finally, it was established that the transcriptional regulation of the RuBIsCo activase 1 gene under biotic stress has the capacity to be employed as a potential stress indicator marker.

Effects of overexpression of the Rubisco small subunit gene under the control of the Rubisco activase promoter on Rubisco contents of rice leaves at different positions

ABSTRACT Photosynthetic activity is expected to be maintained during leaf senescence if the amount of Rubisco is maintained. As the mRNA level of the Rubisco gene decreases rapidly just before the stage of full expansion, its overexpression after full expansion would be effective. We previously found that the mRNA level of the Rubisco activase gene (RCA) is maintained during leaf senescence. In the present study, the Rubisco small subunit gene (RBCS) was overexpressed under the control of the promoter of RCA in rice. Although Rubisco content increased in the uppermost, fully expanded leaves of transgenic plants in comparison with that in wild-type plants, in the penultimate leaves it decreased to a level similar to that of the wild-type plants. In expanding leaves in transgenic plants, the mRNA levels of the transgene RBCS increased further, leading to increases in the mRNA levels of total RBCS and the Rubisco large subunit gene (RBCL). In the uppermost, fully expanded leaves and the penultimate fully expanded leaves, however, the mRNA levels of RBCS2 and total RBCS decreased drastically, and those of RBCL were similar to the wild-type levels. These results indicate that Rubisco content was not maintained during leaf senescence in the transgenic plants. One reason for this is that the expression of RBCS by the RCA promoter was weak in leaves at low positions. We discuss the possible reasons for this unexpected phenomenon.

Improving drought-, salinity-, and heat-tolerance in transgenic plants by co-overexpressing Arabidopsis vacuolar pyrophosphatase gene AVP1 and Larrea Rubisco activase gene RCA

The severity and frequency of many abiotic stresses such as drought, salinity and heat, cause substantial crop losses worldwide, which poses a serious challenge in food security. To increase crop production, new approaches are needed. Previous research has shown that overexpression of the tonoplast H+ pyrophosphatase gene AVP1 leads to improved drought and salt tolerance in transgenic plants. Other research showed that overexpression of thermotolerant ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase gene could maintain photosynthesis at higher temperatures, which contributes to higher heat tolerance in transgenic plants. In nature, abiotic stresses rarely come alone, instead these stresses often occur in various combinations. Therefore, it is desirable to make crops more tolerant to multiple stresses, which will likely lead to higher crop yield under various stress conditions. It is shown here that co-overexpression of the Arabidopsis gene AVP1 and the Larrea Rubisco activase gene RCA significantly increases drought, salinity and heat tolerance, resulting in higher biomass and seed yield than wild-type plants. AVP1/RCA co-overexpressing plants are as more drought- and salt-tolerant as AVP1-overexpressing plants, and as more heat-tolerant as RCA-overexpressing plants. More importantly, they produce higher seed yields than AVP1-overexpressing, RCA-overexpressing, and wild-type plants under combined drought and heat conditions.

Proline-stimulated signaling primarily targets the chlorophyll degradation pathway and photosynthesis associated processes to cope with short-term water deficit in maize.

Increased photosynthetic efficiencies in genotypes with greater proline level and in crops treated with proline under water deficit have been reported in recent years, but the biochemical and molecular mechanisms of this process are still not known. We examined photosystem II (PSII) activity, photosynthetic enzymes, ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco), phosphoenolpyruvate carboxylase (PEPc), rubisco activase (RCA), and chlorophyll metabolic enzymes, magnesium chelatase (Mg-CHLI), and chlorophyllase (Chlase), which would be the primary targets of exogenous proline to provide photosynthetic protection to plants under PEG-induced short-term water deficit. Two maize genotypes W23/M14 with greater proline content and Şafak with low proline content were hydroponically grown for 21-23days, and then the seedlings were subjected to water deficit (- 0.75MPa) induced by PEG6000 for 0, 4, and 8h. Before the seedlings were exposed to the water deficit, proline (1mM) was applied to the rooting medium of the Şafak genotype for 2days. The time course effects of the applications showed that exogenous proline significantly enhanced PSII efficiency, PEPc activity, rubisco activity, and the relative expression levels of PEPc, rubisco large subunit, rubisco small subunit, and RCA genes at 0, 4, and 8h. The W23/M14 genotype had higher rubisco quantity than the Şafak genotype at all time periods. Proline pre-treatment under the stress-free and PEG conditions reduced the activity of Chlase and the gene expressions of Chlase, while it enhanced Mg-CHLI gene expression at 0, 4, and 8h. Taken together, the results indicated that the primary target of proline-stimulated signaling in maize seedlings exposed to short-term severe water deficit may be to induce PSII efficiency, activities of carbon dioxide fixation enzymes and chlorophyll metabolism and mitigate chlorophyll degradation.

Effects of Overproduction of Rubisco Activase on Rubisco Content in Transgenic Rice Grown at Different N Levels.

It has been reported that overproduction of Rubisco activase (RCA) in rice (Oryza sativa L.) decreased Rubisco content, resulting in declining photosynthesis. We examined the effects of RCA levels on Rubisco content using transgenic rice with overexpressed or suppressed RCA under the control of different promoters of the RCA and Rubisco small subunit (RBCS) genes. All plants were grown hydroponically with different N concentrations (0.5, 2.0 and 8.0 mM-N). In RCA overproduced plants with > 2-fold RCA content (RCA-HI lines), a 10%–20% decrease in Rubisco content was observed at 0.5 and 2.0 mM-N. In contrast, at 8.0 mM-N, Rubisco content did not change in RCA-HI lines. Conversely, in plants with 50%–60% increased RCA content (RCA-MI lines), Rubisco levels remained unchanged, regardless of N concentration. Such effects on Rubisco content were independent of the promoter that was used. In plants with RCA suppression to < 10% of the wild-type RCA content, Rubisco levels were increased at 0.5 mM-N, but were unchanged at 2.0 and 8.0 mM-N. Thus, the effects of the changes in RCA levels on Rubisco content depended on N supply. Moreover, RCA overproduction was feasible without a decrease in Rubisco content, depending on the degree of RCA production.

Salicylic acid alleviates aluminum-induced inhibition of biomass by enhancing photosynthesis and carbohydrate metabolism in Panax notoginseng

Determine whether salicylic acid (SA) can alleviate the inhibitory effects of Al stress on dry matter accumulation in Panax notoginseng, and to investigate the mechanism by which the SA regulates photosynthesis and carbohydrate metabolism. Effects of SA on the biomass of P. notoginseng and the concentration of Al in leaves under Al stress were evaluated. SA and the scavenger paclobutrazol (PAC, SA synthetic inhibitor) were used to assess the effects of SA on photosynthesis and the metabolism of total nonstructural carbohydrates (TNC) in P. notoginseng. SA reduced Al by 13.23% in the leaves of P. notoginseng under Al stress. It also promoted the synthesis of carbohydrates in the leaves and their transport to the roots. Additionally, SA alleviated the Al-induced reduction of chlorophyll (Chl) by upregulating the expression of Chl synthesis genes (CHLM, CHLG, HEMB1, HEMC, and HEME) and downregulating the degradation genes (CLH2 and PPH1). Concomitantly, the rubisco activase (RCA) and rubisco enzyme activities were promoted by upregulating the expressions of the RCA, rbcL, and rbcS genes via treatment with SA, thereby restoring the synthesis and metabolism of TNC. Furthermore, SA attenuated the decrease in photosynthetic capacity and photosynthesis system II photochemistry efficiency in Al-stressed plants. Furthermore, SA significantly reduced the H2O2 concentration by 12.22% under Al stress. By regulating photosynthesis-related genes and photochemical processes, SA promoted photosynthesis and enhanced leaf carbohydrate synthesis under Al stress. Thus, SA enhanced the production of P. notoginseng biomass, ultimately reducing the inhibitory effects of Al.

Genetic determinants controlling maize rubisco activase gene expression and a comparison with rice counterparts

BackgroundRubisco activase (RCA) regulates the activity of Rubisco and is a key enzyme of photosynthesis. RCA expression was widely reported to affect plant photosynthesis and crop yield, but the molecular basis of natural variation in RCA expression in a wide range of maize materials has not been fully elucidated.ResultsIn this study, correlation analysis in approximately 200 maize inbred lines revealed a significantly positive correlation between the expression of maize RCA gene ZmRCAβ and grain yield. A genome-wide association study revealed both cis-expression quantitative trait loci (cis-eQTLs) and trans-eQTLs underlying the expression of ZmRCAβ, with the latter playing a more important role. Further allele mining and genetic transformation analysis showed that a 2-bp insertion and a 14-bp insertion in the promoter of ZmRCAβ conferred increased gene expression. Because rice is reported to have higher RCA gene expression than does maize, we subsequently compared the genetic factors underlying RCA gene expression between maize and rice. The promoter activity of the rice RCA gene was shown to be stronger than that of the maize RCA gene, suggesting that replacing the maize RCA gene promoter with that of the rice RCA gene would improve the expression of RCA in maize.ConclusionOur results revealed two DNA polymorphisms regulating maize RCA gene ZmRCAβ expression, and the RCA gene promoter activity of rice was stronger than that of maize. This work increased understanding of the genetic mechanism that underlies RCA gene expression and identify new targets for both genetic engineering and selection for maize yield improvement.

Changes in content of steroid regulators during cold hardening of winter wheat - Steroid physiological/biochemical activity and impact on frost tolerance

The purpose of experiments was to describe the alterations of content of steroid regulators (brassinosteroids, progesterone) during cold hardening of winter wheat. Further we studied physiological and biochemical changes induced by these steroids in cold hardened winter wheat together with estimation of plant frost tolerance. The endogenous brassinosteroid content was elevated in winter wheat during cold hardening while level of progesterone was lowered. A higher content of brassinosteroids (but not progesterone) was connected to better frost tolerance of winter wheat cultivars. Plant supplementation with brassinosteroid (24-epibrassinolide) and progesterone before cold hardening reduced frost damage. Tests with the inhibitors of the biosynthesis of brassinosteroids and progesterone suggested that these steroids are one of players in regulating the antioxidant system in winter wheat during cold hardening. Their role in regulating the expression of Rubisco or the Rubisco activase gene was less clear. Steroid regulators did not affect the content of the stress hormone ABA. Model studies of the membranes, made on a Langmuir bath, showed an increase in the value of the parameter describing differences in membrane compressibility (resulting from stronger interactions among the molecules in the monolayers). This suggests that 24-epibrassinolide and progesterone enter into the lipid layer and - in a similar way to sterols – stabilise the interaction among lipids. It may be significant step for better frost tolerance. The use of steroid regulators (especially brassinosteroids) as agrochemicals improving frost tolerance of winter cereals will be discussed.

RuBisCo activase—a catalytic chaperone involved in modulating the RuBisCo activity and heat stress-tolerance in wheat

RuBisCo activase modulate the activity of RuBisCo and protect the nascent proteins from aggregation under heat stress (HS). Here, we have identified and cloned a putative RuBisCo activase (Rca) gene of 1402 bp from wheat cv. HD2985 using transcriptomic approach. Evolutionary search established the presence of 63 Orthologs and 2 Paralogs of the cloned Rca gene. Sequence analysis showed significant variations in the amino acid of Rca and RuBisCo (large and small subunit) in thermotolerant and thermosusceptible wheat cvs. Heterologous expression of Rca in E. coli showed the release of ~ 47 kDa purified protein. Expression analysis of Rca at transcript and protein level showed significant up-regulation in wheat cvs. Raj3765 (thermotolerant) and HD2329 (thermosusceptible) under HS. RuBisCo enzyme present in thermosusceptible cv. showed more sensitivity to HS, as compared to thermotolerant. Rca activity was observed higher in Raj3765 during pollination and milky-ripe stages under HS (38 °C, 1 h), as compared to HD2329. The binding of Rca with the RuBisCo under HS was observed more stable in Raj3765, as compared to HD2329. The purified Rca enzyme was observed more effective in the renaturation of RuBisCo (inactive) under HS in Raj3765 than in HD2329. A positive correlation was established between the Rca enzyme activity and radical scavenging potential in the leaves of both the wheat cvs. under HS. There is a need to characterize the enzyme kinetics and functional diversity of Rca in order to exploit it in a better way to augment the carbon assimilatory processes in wheat under differential HS.

Evolution of Rubisco activase gene in plants.

Rubisco activase of plants evolved in a stepwise manner without losing its function to adapt to the major evolutionary events including endosymbiosis and land colonization. Rubisco activase is an essential enzyme for photosynthesis, which removes inhibitory sugar phosphates from the active sites of Rubisco, a process necessary for Rubisco activation and carbon fixation. The gene probably evolved in cyanobacteria as different species differ for its presence. However, the gene is present in all other plant species. At least a single gene copy was maintained throughout plant evolution; but various genome and gene duplication events, which occurred during plant evolution, increased its copy number in some species. The exons and exon-intron junctions of present day higher plant's Rca, which is conserved in most species seem to have evolved in charophytes. A unique tandem duplication of Rca gene occurred in a common grass ancestor, and the two genes evolved differently for gene structure, sequence, and expression pattern. At the protein level, starting with a primitive form in cyanobacteria, RCA of chlorophytes evolved by integrating chloroplast transit peptide (cTP), and N-terminal domains to the ATPase, Rubisco recognition and C-terminal domains. The redox regulated C-terminal extension (CTE) and the associated alternate splicing mechanism, which splices the RCA-α and RCA-β isoforms were probably gained from another gene in charophytes, conserved in most species except the members of Solanaceae family.

Overexpression of the rubisco activase gene improves growth and low temperature and weak light tolerance in Cucumis sativus.

Rubisco activase (RCA) is an important enzyme that can catalyze the carboxylation and oxygenation activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which is involved in the photosynthetic carbon reduction cycle. Here, we studied the effects of changes in RCA activity on photosynthesis, growth and development, as well as the low temperature and weak light tolerance of RCA overexpressing transgenic cucumber (Cucumis sativus) plants. CsRCA overexpression increased the plant height, leaf area and dry matter, and decreased the root/top ratio in transgenic cucumber plants compared with the wild-type (WT) plants. Low temperature and low light stress led to decreases in the CsRCA expression and protein levels, the photosynthetic rate (Pn) and the stomatal conductance (Gs), but an increase in the intercellular CO2 (Ci) concentration in cucumber leaves. The actual photochemical efficiency and maximal photochemical efficiency of photosystem II in cucumber seedlings also declined, but the initial fluorescence increased during low temperature and weak light stress. Transgenic plants showed a lower decrease in the CsRCA expression level and actual and maximal photochemical efficiencies, as well as increases in the Ci and initial fluorescence relative to the WT plants. Low temperature and low light stress resulted in a significant increase in the malondialdehyde (MDA) content; however, this increase was reduced in transgenic plants compared with that in WT plants. Thus, the overexpression of CsRCA may promote the growth and low temperature and low light tolerance of cucumber plants in solar greenhouses.

Effects of 2,4-epibrassinolide on photosynthesis and Rubisco activase gene expression in Triticum aestivum L. seedlings under a combination of drought and heat stress

We examined the effects of 2,4-epibrassinolide (EBR) application on photosynthesis, antioxidant enzyme activity, and Rubisco activase (RCA) gene expression in wheat (Triticum aestivum L.) seedlings under a combination of drought and heat stress. The net photosynthetic rates (Pn) of wheat seedlings decreased significantly, the photosynthetic capability was inhibited, and the activities of superoxide (SOD), peroxidase (POD), catalase (CAT), and RCA as well as the initial and total activity of Rubisco declined under the combined stress. These decreases and inhibitory effects were significantly ameliorated by exogenous EBR application. Three subunits (45–46, 41–42, and 38–39 kDa) of RCA were observed in wheat seedlings. The abundances of the 38–39 kDa and 41–42 kDa subunits were significantly lower in plants subjected to stressful conditions than in unstressed plants. Interestingly, a marked increase in 45–46 kDa RCA was observed under heat or heat combined with drought stress. The abundance of 38–39 kDa RCA in seedlings exposed to heat, drought, or their combination was significantly enhanced by EBR pretreatment, which paralleled the changes in initial Rubisco activity and Pn, but was not consistent with observed mRNA abundance. These results indicated that the larger subunit of RCA (45–46 kDa), which is more thermostable and increased in response to moderate heat stress, and the smaller isoform (38–39 kDa) of RCA may play important roles in maintaining the photosynthetic capability by EBR under stress conditions.

Cloning and expression analysis of Rubisco activase genes in Carya cathayensis

ABSTRACTRibulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a key enzyme involved in CO2 assimilation during photosynthesis. Rubisco activation depends on the activity of Rubisco activase (RCA). We performed 3′/5′ rapid amplification of cDNA ends (RACE) and reverse transcription polymerase chain reaction (RT-PCR) to amplify the 3′ and 5′ end sequences of RCA genes from hickory. We obtained two full-length gene sequences, designated CcRCAα and CcRCAβ. The two corresponding cDNAs are divergent in both the translated and 3′ untranslated regions. The analysis of the genomic DNA sequences suggested that the corresponding mRNAs are transcripts of two different genes and not the products of a single alternatively spliced pre-mRNA. We examined the expression of CcRCAα and CcRCAβ in hickory leaves at various stages of development by quantitative real-time PCR (qRT-PCR) analysis. The results suggest that RCA genes play an important role in development and environmental responses. These results provide a basis for modulating RCA gene expression to improve the photosynthetic rate and plant growth in hickory.

Expression quantitative trait loci analysis of the Rubisco activase gene in maize

Expression quantitative trait loci (eQTL) analyses were applied in order to identify genetic factors that are relevant to the expression of a β-isoform Rubisco activase gene in maize, namely ZmRCAβ, in this study. During two years, a maize recombinant inbred line population was measured for ZmRCAβ expression levels at the grain filling stage. Based on a genetic map containing 916 molecular markers, we detected five eQTLs, namely qRCA2.1 on chromosome 2, and qRCA4.1, qRCA4.2, qRCA4.3, and qRCA4.4 on chromosome 4. These eQTLs explained the phenotypic variation ranging from 6.14% to 7.50% with the logarithm of the odd values ranging from 3.11 to 4.96. Based on the position of the eQTLs and ZmRCAβ on the chromosome, qRCA4.2 was inferred as a cis-eQTL and the remaining as a trans-eQTL, suggesting that a combination of both cis- and trans-acting elements might control ZmRCAβ expression. qRCA4.2, qRCA4.3, and qRCA4.4 were repeatedly detected during two years.

Identification of Two bZIP Transcription Factors Interacting with the Promoter of Soybean Rubisco Activase Gene (GmRCAα).

Rubisco activase (RCA), a key photosynthetic protein, catalyses the activation of Rubisco and thus plays an important role in photosynthesis. Although the RCA gene has been characterized in a variety of species, the molecular mechanism regulating its transcription remains unclear. Our previous studies on RCA gene expression in soybean suggested that expression of this gene is regulated by trans-acting factors. In the present study, we verified activity of the GmRCAα promoter in both soybean and Arabidopsis and used a yeast one-hybrid (Y1H) system for screening a leaf cDNA expression library to identify transcription factors (TFs) interacting with the GmRCAα promoter. Four basic leucine zipper (bZIP) TFs, GmbZIP04g, GmbZIP07g, GmbZIP1, and GmbZIP71, were isolated, and GmbZIP04g and GmbZIP07g were confirmed as able to bind to a 21-nt G-box-containing sequence. Additionally, the expression patterns of GmbZIP04g, GmbZIp07g, and GmRCAα were analyzed in response to abiotic stresses and during a 24-h period. Our study will help to advance elucidation of the network regulating GmRCAα transcription.