The crosstalk between gibberellin(GA)and abscisic acid(ABA)signaling is crucial for balancing plant growth and adaption to environmental stress.Nevertheless,the molecular mechanism of their mutual antagonism still rem...The crosstalk between gibberellin(GA)and abscisic acid(ABA)signaling is crucial for balancing plant growth and adaption to environmental stress.Nevertheless,the molecular mechanism of their mutual antagonism still remains to be fully claried.In this study,we found that knockout of the rice NAC(NAM,ATAF1/2,CUC2)tran-scription factor gene OsNAC120 inhibits plant growth but enhances drought tolerance,whereas OsNAC120 overexpression produces the opposite results.Exogenous GA can rescue the semi-dwarf phenotype of osnac120 mutants,and further study showed that OsNAC120 promotes GA biosynthesis by transcriptionally activating the GA biosynthetic genes OsGA20ox1 and OsGA20ox3.The DELLA protein SLENDER RICE1(SLR1)interacts with OsNAC120 and impedes its transactivation ability,and GA treatment can remove the inhi-bition of transactivation activity caused by SLR1.On the other hand,OsNAC120 negatively regulates rice drought tolerance by repressing ABA-induced stomatal closure.Mechanistic investigation revealed that OsNAC120 inhibits ABA biosynthesis via transcriptional repression of the ABA biosynthetic genes OsNCED3 and OsNCED4.Rice OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9(OsSAPK9)physically interacts with OsNAC120 and mediates its phosphorylation,which results in OsNAC120 degradation.ABA treatment ac-celerates OsNAC120 degradation and reduces its transactivation activity.Together,our findings provide evidence that OsNAC120 plays critical roles in balancing GA-mediated growth and ABA-induced drought tolerance in rice.This research will help us to understand the mechanisms underlying the trade-off between plant growth and stress tolerance and to engineer stress-resistant,high-yielding crops.展开更多
Seed vigor is a key factor affecti ng seed quality.The mechanical drying process exerts a sign ificant in fluence on rice seed vigor.The initial moisture con tent(IMC)and drying temperature are considered the main fac...Seed vigor is a key factor affecti ng seed quality.The mechanical drying process exerts a sign ificant in fluence on rice seed vigor.The initial moisture con tent(IMC)and drying temperature are considered the main factors affecting rice seed vigor through mechanical drying.This study aimed to determine the optimum drying temperature for rice seeds according to the IMC,and elucidate the mechanisms mediating the effects of drying temperature and IMC on seed vigor.Rice seeds with three different IMCs(20%,25%,and 30%)were dried to the target moisture content(14%)at four different drying temperatures.The results showed that the drying temperature and IMC had significant effects on the drying performance and vigor of the rice seeds.The upper limits of drying temperature for rice seeds with 20%,25%,and 30%IMCs were 45,42,and 38°C,respectively.The drying rate and seed temperature increased sign ificantly with in creasing drying temperature.The drying temperature,drying rate,and seed temperature showed extremely significant negative correlations with germination energy(GE),germination rate,germination index(Gl),and vigor index(VI).A high IMC and drying temperature probably induced a massive accumulation of hydrogen peroxide(H2O2)and superoxide anions in the seeds,enhanced superoxide dismutase(SOD)and catalase(CAT)activity,and increased the abscisic acid(ABA)content.In the early stage of seed germination,the IMC and drying temperature regulated seed germination through the metabolism of H2O2,gibberellin acid(GA),ABA,and a-amylase.These results indicate that the metabolism of reactive oxygen species(ROS),antioxidant enzymes,GA,ABA,and a-amylase might be involved in the mediation of the effects of drying temperature on seed vigor.The results of this study provide a theoretical basis and technical guidance for the mechanical drying of rice seeds.展开更多
Seed dormancy is an important agronomic trait in cereals. Using deep dormant （N22）, medium dormant （ZH11）, and non-dormant （G46B） rice cultivars, we correlated seed dormancy phenotypes with abscisic acid （ABA）...Seed dormancy is an important agronomic trait in cereals. Using deep dormant （N22）, medium dormant （ZH11）, and non-dormant （G46B） rice cultivars, we correlated seed dormancy phenotypes with abscisic acid （ABA） and gibberellin （GA） metabolism gene expression profiles and phytohormone levels during seed development and imbibition. A time course analysis of ABA and GA content during seed development showed that N22 had a high ABA level at early and middle seed developmental stages, while at late developmental stage it declined to the level of ZHll; however, its ABA/GA ratio maintained at a high level throughout seed development. By contrast, G46B had the lowest ABA content during seed development though at early developmental stage its ABA level was close to that of ZH11, and its ABA/GA ratio peaked at late developmental stage that was at the same level of ZHll. Compared with N22 and G46B, ZH11 had an even and medium ABA level during seed development and its ABA/GA ratio peaked at the middle developmental stage. Moreover, the seed development time-point having high ABA/GA ratio also had relatively high transcript levels for key genes in ABA and GA metabolism pathways across three cultivars. These indicated that the embryo-imposed dormancy has been induced before the late developmental stage and is determined by ABA/GA ratio. A similar analysis during seed imbibition showed that ABA was synthesized in different degrees for the three cultivars. In addition, water uptake assay for intact mature seeds suggested that water could permeate through husk barrier into seed embryo for all three cultivars; however, all three cultivars showed distinct colors by vanillin-staining indicative of the existence of flavans in their husks, which are dormancy inhibition compounds responsible for the husk-imposed dormancy.展开更多
基金supported by the National Natural Science Foundation of China (32071985)the Chongqing Special Key Project for Technological Innovation and Application Development (CSTB2022TIAD-KPX0018,CSTB2022TIAD-KPX0016,CSTB2022TIAD-KPX0015).
文摘The crosstalk between gibberellin(GA)and abscisic acid(ABA)signaling is crucial for balancing plant growth and adaption to environmental stress.Nevertheless,the molecular mechanism of their mutual antagonism still remains to be fully claried.In this study,we found that knockout of the rice NAC(NAM,ATAF1/2,CUC2)tran-scription factor gene OsNAC120 inhibits plant growth but enhances drought tolerance,whereas OsNAC120 overexpression produces the opposite results.Exogenous GA can rescue the semi-dwarf phenotype of osnac120 mutants,and further study showed that OsNAC120 promotes GA biosynthesis by transcriptionally activating the GA biosynthetic genes OsGA20ox1 and OsGA20ox3.The DELLA protein SLENDER RICE1(SLR1)interacts with OsNAC120 and impedes its transactivation ability,and GA treatment can remove the inhi-bition of transactivation activity caused by SLR1.On the other hand,OsNAC120 negatively regulates rice drought tolerance by repressing ABA-induced stomatal closure.Mechanistic investigation revealed that OsNAC120 inhibits ABA biosynthesis via transcriptional repression of the ABA biosynthetic genes OsNCED3 and OsNCED4.Rice OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9(OsSAPK9)physically interacts with OsNAC120 and mediates its phosphorylation,which results in OsNAC120 degradation.ABA treatment ac-celerates OsNAC120 degradation and reduces its transactivation activity.Together,our findings provide evidence that OsNAC120 plays critical roles in balancing GA-mediated growth and ABA-induced drought tolerance in rice.This research will help us to understand the mechanisms underlying the trade-off between plant growth and stress tolerance and to engineer stress-resistant,high-yielding crops.
基金Key Research and Development Program of Zhejiang Province(No.2019C02011)the“San Nong Liu Fang”Science and Technology Cooperation Project of Zhejiang Province(No.2018SNLF004),China。
文摘Seed vigor is a key factor affecti ng seed quality.The mechanical drying process exerts a sign ificant in fluence on rice seed vigor.The initial moisture con tent(IMC)and drying temperature are considered the main factors affecting rice seed vigor through mechanical drying.This study aimed to determine the optimum drying temperature for rice seeds according to the IMC,and elucidate the mechanisms mediating the effects of drying temperature and IMC on seed vigor.Rice seeds with three different IMCs(20%,25%,and 30%)were dried to the target moisture content(14%)at four different drying temperatures.The results showed that the drying temperature and IMC had significant effects on the drying performance and vigor of the rice seeds.The upper limits of drying temperature for rice seeds with 20%,25%,and 30%IMCs were 45,42,and 38°C,respectively.The drying rate and seed temperature increased sign ificantly with in creasing drying temperature.The drying temperature,drying rate,and seed temperature showed extremely significant negative correlations with germination energy(GE),germination rate,germination index(Gl),and vigor index(VI).A high IMC and drying temperature probably induced a massive accumulation of hydrogen peroxide(H2O2)and superoxide anions in the seeds,enhanced superoxide dismutase(SOD)and catalase(CAT)activity,and increased the abscisic acid(ABA)content.In the early stage of seed germination,the IMC and drying temperature regulated seed germination through the metabolism of H2O2,gibberellin acid(GA),ABA,and a-amylase.These results indicate that the metabolism of reactive oxygen species(ROS),antioxidant enzymes,GA,ABA,and a-amylase might be involved in the mediation of the effects of drying temperature on seed vigor.The results of this study provide a theoretical basis and technical guidance for the mechanical drying of rice seeds.
基金supported by the grants from the Ministry of Science and Technology of the People’s Republic of China (No. 2012CB944800)the National Natural Science Foundation of China (Nos. 31271680 and 91335203)
文摘Seed dormancy is an important agronomic trait in cereals. Using deep dormant （N22）, medium dormant （ZH11）, and non-dormant （G46B） rice cultivars, we correlated seed dormancy phenotypes with abscisic acid （ABA） and gibberellin （GA） metabolism gene expression profiles and phytohormone levels during seed development and imbibition. A time course analysis of ABA and GA content during seed development showed that N22 had a high ABA level at early and middle seed developmental stages, while at late developmental stage it declined to the level of ZHll; however, its ABA/GA ratio maintained at a high level throughout seed development. By contrast, G46B had the lowest ABA content during seed development though at early developmental stage its ABA level was close to that of ZH11, and its ABA/GA ratio peaked at late developmental stage that was at the same level of ZHll. Compared with N22 and G46B, ZH11 had an even and medium ABA level during seed development and its ABA/GA ratio peaked at the middle developmental stage. Moreover, the seed development time-point having high ABA/GA ratio also had relatively high transcript levels for key genes in ABA and GA metabolism pathways across three cultivars. These indicated that the embryo-imposed dormancy has been induced before the late developmental stage and is determined by ABA/GA ratio. A similar analysis during seed imbibition showed that ABA was synthesized in different degrees for the three cultivars. In addition, water uptake assay for intact mature seeds suggested that water could permeate through husk barrier into seed embryo for all three cultivars; however, all three cultivars showed distinct colors by vanillin-staining indicative of the existence of flavans in their husks, which are dormancy inhibition compounds responsible for the husk-imposed dormancy.
