| In agricultural production,phosphorus is a large amount of nutrients required for plant growth,and the shortage of available phosphorus in soil is an important environmental factor that limits plant growth and yield.When plants suffer under phosphorus deficiency conditions,the change of root structure is conducive to enhancing the ability of plants to obtain phosphorus from the environment,and membrane lipid remodeling will help to enhance the reutilization capacity of phosphorus in cells.ZmSQD2.1 and ZmSQD2.2 can improve the low phosphorus tolerance of Arabidopsis thalianaUnder phosphorus deficiency,plants can remodel membrane lipids useing non-phosphoglycerides such as sulfoquinovosyldiacylglycerol(SQDG)and digalactosyldiacylglycerol(DGDG)to replace membrane phospholipids,and increase the utilization of Pi in the cell.In plant chloroplasts,SQD2 is a crucial enzyme in synthesising the SQDG pathway,which catalyzes the formation of SQDG from UDP-SQ and diacylglycerol(DAG).In this study,ZmSQD2.1,ZmSQD2.2,and ZmSQD2.4 from maize were used as the research objects,and their biological functions of low phosphorus tolerance were preliminarily explored.Arabidopsis grown under phosphorus deficiency conditions for 50 days.The overexpressed ZmSQD2.1 and ZmSQD2.2 Arabidopsis plants had larger rosette leaf area than the wild-type control and the Atsqd2 mutant,and the rosette leaf area of Atsqd2 mutants is the smallest.Compared with the wild-type control or the Atsqd2 mutant,the overexpressed ZmSQD2.1 and ZmSQD2.2 Arabidopsis significantly increased the primary root length,the number of lateral roots,the chlorophyll content,the net photosynthetic rate and the plant biomass.Therefore,the overexpressed ZmSQD2.1 and ZmSQD2.2 Arabidopsis showed better low phosphorus tolerance.Compared with the wild-type control,the overexpressed ZmSQD2.4 Arabidopsis had no difference in primary root length,the number of lateral roots,the chlorophyll content,the net photosynthetic rate and the plant biomass,and did not show low phosphorus tolerance under phosphorus deficiency.Under different concentrations of NaCl and mannitol,there was no difference in seed germination rate,cotyledon greening rate,primary root length and biomass of overexpressed Arabidopsis ZmSQD2.1,ZmSQD2.2,ZmSQD2.4 compared with wild type.The experimental results preliminarily suggested that ZmSQD2.1,ZmSQD2.2 and ZmSQD2.4 could not improve the salt and drought resistance of Arabidopsis in the seed germination stage.In summary,ZmSQD2.1 and ZmSQD2.2 improved the tolerance of Arabidopsis to phosphorus deficiency,which can be used as candidate genes for plant low phosphorus tolerance genetic engineering.Overexpressed TsVP cotton increased root biomass and seed cotton yield under phosphorus deficiencyThe root architecture of plants under phosphorus deficiency will change,showing that the growth of the primary roots is hindered,and the formation of lateral roots and root hairs is promoted to increase its absorption surface area in the soil,thereby enhancing nutrient absorption and improving the production performance under mineral nutrition stress.In this study,the transgenic cotton plant that overexpressed Thellungiella halophila H+-PPase gene TsVP was used as the material,and the characteristics of low phosphorus tolerance of the overexpressed TsVP cotton were explored through hydroponics,sand culture and soil cultured potted,which provided candidate genes for cultivating low phosphorus tolerant plants and new materials for cultivating low phosphorus tolerant cotton.The seed yield of soil cultured potted cotton was measured,and the seed yield of transgenic TsVP cotton was significantly higher than that of the wild type control under phosphorus deficiency conditions,with an increase of up to 34.68%.The overexpressed TsVP cotton’s ability to cope with the low phosphorus stress is higher than the wild type control.The leaf photosynthetic and PSII performance of soil cultured potted cotton at the boll stage were measured under phosphorus deficiency conditions.Compared with cotton grown under sufficient phosphorus,the carbon assimilation capacity(Pn)and PSII performance of cotton leaves under phosphorus deficiency conditions were significantly decreased.The overexpressed TsVP cotton has higher photosynthetic performance and PSII performance than the wild type control under phosphorus deficiency conditions,which is reflected in its higher Pn,Fv/Fm and PI abs,and Rubisco carboxylase activity and ATP content,NADPH content and RuBP content were higher,so the transgenic cotton showed higher dark reaction performance.Therefore,the leaves of transgenic cotton had higher ATP and NADPH synthesis ability,RuBP regeneration ability and carbon dioxide assimilation ability than wild type control under phosphorus deficiency,which increased the low phosphorus tolerance of transgenic cotton.The concentration of Pi in cotton leaves at the five-leaf-one-core stage was measured in hydroponics,sand and soil culture experiments.Transgenic cotton had a higher Pi concentration than the wild type control under sufficient or phosphorus deficiency conditions.In potted cotton,the Pi of transgenic cotton leaves increased reach up to 11.33%under sufficient phosphorus,and the Pi of transgenic cotton leaves increased reach up to 32.59%under phosphorus deficiency.The results of Pi concentration determination in cotton leaves showed that overexpression of TsVP in cotton improved the uptake of phosphorus from the environment by cotton and increased Pi levels in leaves.The biomass of cotton roots in hydroponic,sand culture and soil culture experiments was measured.Under the condition of sufficient phosphorus or phosphorus deficiency,the overexpressed TsVP cotton had a more developed root than the wild type control,and the root biomass and the number of lateral roots of the transgenic cotton were significantly higher than that of the wild type control.In potted cotton,the root dry weight of transgenic cotton increased by up to 27.54%under sufficient phosphorus and up to 41.15%under phosphorus deficiency.The results showed that overexpression of TsVP cotton improved root architecture.Under phosphorus deficiency,the transgenic cotton has no difference in the affinity of the transport protein to Pi(Km,Cmin)compared with the wild type control.However,the speed of Pi influx into the cell is faster.That is,the maximum uptake rate Imax of the transgenic cotton is significantly higher than that of the wild type control,which showed that transgenic cotton plants have a more developed root,which is beneficial for plants to obtain phosphorus from the environment,and are more tolerant to phosphorus deficiency than wild type plants.The expression levels of genes related to polar auxin transport,root tip stem cell maintenance and lateral root development of sand-cultured cotton tips were determined.Under sufficient phosphorus or phosphorus deficiency,the expression of genes GhAUX3,GhPIN1a and GhPIN1c related to auxin transport in the root tip of overexpressed TsVP cotton were up regulated compared with the wild type control.In addition,the expression of genes GhPLT2,GhRGF2,GhTPST,GhSCR and GhSHR,etc.related to auxin transport was up-regulated.Furthermore,the expression of genes GhARF19,GhEIN3,GhLPR1,GhPDR2 and GhTIR1 related to lateral root development was up regulated,indicating that transgenic plants have a more developed root that may be related to the auxin polar transport,maintenance of root tip stem cells,and up-regulated of expression of genes related to lateral root development.In summary,under phosphorus deficiency,the overexpression of TsVP led to the high level expression of some genes related to auxin polar transport,root tip stem cell maintenance and lateral root development in transgenic cotton,and the transgenic cotton had a more developed root,thereby enhancing the ability to absorb Pi from the environment in transgenic cotton,improving the level of inorganic phosphorus and photosynthetic ability of leaves,and increasing the yield of the seed of transgenic cotton under low phosphorus,which made transgenic cotton to show high tolerance to low phosphorus. |
