Response of Glutathione and Glutathione S-transferase in Rice Seedlings Exposed to Cadmium Stress

A hydroponic culture experiment was done to investigate the effect of Cd stress on glutathione content （GSH） and glutathione S-transferase （GST, EC 2.5.1,18） activity in rice seedlings. The rice growth was severely inhibited when Cd level in the solution was higher than 10 mg/L. In rice shoots, GSH content and GST activity increased with the increasing Cd level, while in roots, GST was obviously inhibited by Cd treatments, Compared with shoots, the rice roots had higher GSH content and GST activity, indicating the ability of Cd detoxification was much higher in roots than in shoots. There was a significant correlation between Cd level and GSH content or GST activity, suggesting that both parameters may be used as biomarkers of Cd stress in rice.

Genetic control of compound leaf development in the mungbean(Vigna radiata L.)

Many studies suggest that there are distinct regulatory processes controlling compound leaf development in different clades of legumes.Loss of function of the LEAFY(LFY)orthologs results in a reduction of leaf complexity to different degrees in inverted repeat-lacking clade(IRLC)and non-IRLC species.To further understand the role of LFY orthologs and the molecular mechanism in compound leaf development in non-IRLC plants,we studied leaf development in unifoliate leaf(un)mutant,a classical mutant of mungbean(Vigna radiata L.),which showed a complete conversion of compound leaves into simple leaves.Our analysis revealed that UN encoded the mungbean LFY ortholog(VrLFY)and played a significant role in leaf development.In situ RNA hybridization results showed that STM-like KNOXI genes were expressed in compound leaf primordia in mungbean.Furthermore,increased leaflet number in heptafoliate leaflets1(hel1)mutants was demonstrated to depend on the function of VrLFY and KNOXI genes in mungbean.Our results suggested that HEL1 is a key factor coordinating distinct processes in the control of compound leaf development in mungbean and its related non-IRLC legumes.

Hydrogen sulfide-linked persulfidation of ABI4 controls ABA responses through the transactivation of MAPKKK18 in Arabidopsis

Hydrogen sulfide(H2S)is a signaling molecule that regulates plant hormone and stress responses.The phytohormone abscisic acid(ABA)plays an important role in plant adaptation to unfavorable environmental conditions and induces the persulfidation of L-CYSTEINE DESULFHYDRASE1(DES1)and the production of H2S in guard cells.However,it remains largely unclear how H2S and protein persulfidation participate in the relay of ABA signals.In this study,we discovered that ABSCISIC ACID INSENSITIVE 4(ABI4)acts downstream of DES1 in the control of ABA responses in Arabidopsis.ABI4 undergoes persulfidation at Cys250 that is triggered in a time-dependent manner by ABA,and loss of DES1 function impairs this process.Cys250 and its persulfidation are essential for ABI4 function in the regulation of plant responses to ABA and the H2S donor NaHS during germination,seedling establishment,and stomatal closure,which are abolished in the ABI4Cys250Ala mutated variant.Introduction of the ABI4Cys250Ala variant into the abi4 des1 mutant did not rescue its hyposensitivity to ABA.Cys250 is critical for the binding of ABI4 to its cognate motif in the promoter of Mitogen-Activated Protein Kinase Kinase Kinase 18(MAPKKK18),which propagates the MAPK signaling cascade induced by ABA.Furthermore,the DES1-mediated persulfidation of ABI4 enhances the transactivation activity of ABI4 toward MAPKKK18,and ABI4 can bind the DES1 promoter,forming a regulatory loop.Taken together,these findings advance our understanding of a post-translational regulatory mechanism and suggest that ABI4 functions as an integrator of ABA and MAPK signals through a process in which DES1-produced H2S persulfidates ABI4 at Cys250.

Rice GLUTATHIONE PEROXIDASE1-mediated oxidation of bZIP68 positively regulates ABA-independent osmotic stress signaling

Osmotic stress caused by drought and high salinity is a significant environmental threat that limits plant growth and agricultural yield. Redox regulation plays an important role in plant stress responses, but the mechanisms by which plants perceive and transduce redox signals are still underexplored. Here, we report a critical function for the thiol peroxidase GPX1 in osmotic stress response in rice, where it serves as a redox sensor and transducer. GPX1 is quickly oxidized upon exposure to osmotic stress and forms an intramolecular disulfide bond, which is required for the activation of bZIP68, a VRE-like basic leucine zipper (bZIP) transcription factor involved in the ABA-independent osmotic stress response pathway. The disulfide exchange between GPX1 and bZIP68 induces homo-tetramerization of bZIP68 and thus positively regulates osmotic stress response by regulating osmotic-responsive gene expression. Furthermore, we discovered that the nuclear translocation of GPX1 is regulated by its acetylation under osmotic stress. Taken together, our findings not only uncover the redox regulation of the GPX1-bZIP68 module during osmotic stress but also highlight the coordination of protein acetylation and redox signaling in plant osmotic stress responses.

The impacts of warming and nitrogen addition on competitive ability of native and invasive populations of Plantago virginica

Aims Global change factors(e.g.warming and nitrogen deposition)may influence biological invasions,but how these factors may influence the performance of invasive species and further mediate the interactions with native competitors remain still unknown.Methods Here,we conducted a 5-month greenhouse experiment to examine the effects of warming(using open-top chambers,+0.62°C)and N addition(adding NH4NO3 at a rate of 4.2 g m−2)on the performance of the native and invasive populations of an invasive species Plantago virginica in competition with a native Plantago asiatica.Important Findings Under warming treatment and its interaction with nitrogen addition treatment(W×N),invasive and native populations of P.virginica had different biomass allocation strategies to compete with native competitor P.asiatica.Native population of P.virginica(PV-Na)increased more below-ground biomass,whereas those from the invasive population(PV-In)increased more above-ground biomass.We also found that invasive species P.virginica had stronger responses to warming and N addition than the native species P.asiatica.The competitive ability of the invasive plants was significantly reduced by warming which indicated that the invasive plant were much stronger sensitivity to elevated temperature than native plant.Similarly,N addition and W×N reduced the competitive response of PV-In in below-ground biomass,but increased the competitive response of PV-Na in above-ground and total biomass when they grew with the P.asiatica.The results show that P.virginica have occurred differential biomass allocation strategies during its invasions and invasive population exhibit flexible competition ability to adapt to environmental changes(especially warming).These findings may potentially help to predict plant invasions and make management strategies in a world with changing climate.

Transcriptional and Post-transcriptional Modulation of SQU and KEW Activities in the Control of Dorsal-Ventral Asymmetric Flower Development in Lotus japonicus

In Papilionoideae legume, Lotusjaponicus, the development of dorsal-ventral （DV） asymmetric flowers is mainly controlled by two TB1/CYCLOIDEA/PCF （TCP） genes, SQUARED STANDARD （SQU） and KEELED WINGS IN LOTUS （KEW）, which determine dorsal and lateral identities, respectively. However, the molecular basis of how these two highly homologous genes orchestrate their diverse functions remains unclear. Here, we analyzed their expression levels, and investigated the transcriptional activities of SQUand KEW. We demonstrated that SQU possesses both activation and repression activities, while KEW acts only as an activator. They form homo- and heterodimers, and then collaboraUvely regulate their expression at the transcription level. Furthermore, we identified two types of post-transcriptional modifications, phosphor- ylation and ATP/GTP binding, both of which could affect their transcriptional activities. Mutations in ATP/ GTP binding motifs of SQU and KEW lead to failure of phosphorylation, and transgenic plants bearing the mutant proteins display defective DV asymmetric flower development, indicating that the two conjugate modifications are essential for their diverse functions. Altogether, SQU and KEW activities are precisely modulated at both transcription and post-transcription levels, which might link DV asymmetric flower development to different physiological status and/or signaling pathways.

The OsAMT1.1 gene functions in ammonium uptake and ammoniumepotassium homeostasis over low and high ammonium concentration ranges

Rice （Oryza sativa） grown in paddy fields is an ammonium （NH4^＋）-preferring crop; however, its AMT-type NH4^＋ transporters that mediate root N acquisition have not been well characterized yet. In this study, we analyzed the expression pattern and physiological function of the OsAMT1.1 gene of the AMT1 subfamily in rice. OsAMT1.1 is located in the plasma membrane and is mainly expressed in the root epidermis, stele and mesophyll cells. Disruption of the OsAMTI.1 gene decreased the uptake of NH4^＋, and the growth of roots and shoots under both low NH4^＋ and high NH4^＋ conditions. OsAMT1.1 contributed to the short-term （5 min） ^15NH4^＋ influx rate by approximately one-quarter, irrespective of the NH4^＋ concentration. Knockout of OsAMTI.I significantly decreased the total N transport from roots to shoots under low NH4^＋ conditions. Moreover, compared with the wild type, the osamt1.1 mutant showed an increase in the potassium （K） absorption rate under high NH4^＋ conditions and a decrease under low NH4^＋ conditions. The mutants contained a significantly high concentration of K in both the roots and shoots at a limited K （0.1 mmol/L） supply when NH4^＋ was replete. Taken together, the results indicated that OsAMT1.1 significantly contributes to the NH4^＋ uptake under both low and high NH4^＋ conditions and plays an important role in N-K homeostasis in rice.

Hydrogen sulfide, a signaling molecule in plant stress responses

Gaseous molecules, such as hydrogen sulfide(H_2S)and nitric oxide(NO), are crucial players in cellular and(patho)physiological processes in biological systems. The biological functions of these gaseous molecules, which were first discovered and identified as gasotransmitters in animals, have received unprecedented attention from plant scientists in recent decades. Researchers have arrived at the consensus that H_2S is synthesized endogenously and serves as a signaling molecule throughout the plant life cycle.However, the mechanisms of H_2S action in redox biology is still largely unexplored. This review highlights what we currently know about the characteristics and biosynthesis of H_2S in plants. Additionally,we summarize the role of H_2S in plant resistance to abiotic stress. Moreover, we propose and discuss possible redox-dependent mechanisms by which H_2S regulates plant physiology.

Hydrogen agronomy:research progress and prospects

Agriculture is the foundation of social development.Under the pressure of population growth,natural disasters,environmental pollution,climate change,and food safety,the interdisciplinary"new agriculture"is becoming an important trend of modern agriculture.In fact,new agriculture is not only the foundation of great health and new energy sources,but is also the cornerstone of national food security,energy security,and biosafety.Hydrogen agronomy focuses mainly on the mechanism of hydrogen gas(H2)biology effects in agriculture,and provides a theoretical foundation for the practice of hydrogen agriculture,a component of the new agriculture.Previous research on the biological effects of H2 focused chiefly on medicine.The mechanism of selective antioxidant is the main theoretical basis of hydrogen medicine.Subsequent experiments have demonstrated that H2 can regulate the growth and development of plant crops,edible fungus,and livestock,and enhance the tolerance of these agriculturally important organisms against abiotic and biotic stresses.Even more importantly,H2 can regulate the growth and development of crops by changing the soil microbial community composition and structure.Use of H2 can also improve the nutritional value and postharvest quality of agricultural products.Researchers have also shown that the biological functions of molecular hydrogen are mediated by modulating reactive oxygen species(ROS),nitric oxide(NO),and carbon monoxide(CO)signaling cascades in plants and microbes.This review summarizes and clarifies the history of hydrogen agronomy and describes recent progress in the field.We also argue that emerging hydrogen agriculture will be an important direction in the new agriculture.Further,we discuss several scientific problems in hydrogen agronomy,and suggest that the future of hydrogen agronomy depends on contributions by multiple disciplines.Important future research directions of hydrogen agronomy include hydrogen agriculture in special environments,such as islands,reefs,aircraft,and outer space.

An invading annual plant benefits less from soil biota and has reduced competitive power with a resident grass

Aims Interactions between plants and their soil biota,arbuscular mycorrhizal fungi(AMF)in particular,may play a vital role in the establishment and the range expansion of exotic plants in new environments.However,whether there are post-introduction shifts in dependence on AMF and how dependency interacts with competition remains poorly understood.Methods We conducted a common garden greenhouse experiment to examine how native(USA)and invasive(China)populations of the plant species Plantago virginica,respond to soil biota,and whether these responses change in the presence of a competitor.Important Findings We found that while native populations consistently had a higher AMF colonization rate and benefited from AMF in both biomass and seed production,invasive populations received less benefit from AMF,and even showed reduced biomass with AMF in the presence of a competitor.This low mycorrhizal dependency in invasive populations correlated with greater suppression by an indigenous competitor for the invader.The different responses of the invasive and native populations to AMF suggest that alteration of mycorrhizal dependency has occurred during the invasion of P.virginica into China.Our findings suggest that this reduced dependency incurs a cost during interspecific competition.