The Role Of TAL In Response To Nitrogen Rate And CO₂ Concentrations In Rice

The yield of rice is mainly composed of the number of panicles per unit area,number of spikelets per panicle,seed setting rate and 1000-grain weight.It is important to know how to improve the yield potential of rice by combining genetic effects with cultivation management and environmental factors.This study focused on the role of a TAL(transaldolase-like)gene by comparing its low expression line(RNA interference,RNAi),wild type(Wuyunjing 7,WT),and overexpression(OX)line.Cultivation factors such as planting density,nitrogen(N)rate and environmental factor CO2 concentration were combined in various treatments to detect the role of TAL gene in the responses in biomass accumulation and yield formation.Our objective was to seek for a theoretical approach to further raising the yield limit.The main findings are as follows.1.Yield and its componentsField experiment reveals that the yield and panicle number of high-density were higher than that of low-density planting.The number of spikelets per panicle in low-density treatment was more than that of high-density treatment.Along with the increase of N rate,the yield and number of panicles increased under low-density treatment.Whereas under high-density treatment,the yield and panicle number increased at low N rate but decreased at higher N rate;With the increase of TAL expression level,the seed setting rate increased during low N rate(N0,N10).At high N rate(N20,N30),alteration of TAL expression level decreased the seed setting rate;At higher expression level of TAL gene,the yield,number of spikelets per panicle and 1000-grain weight increased.In the pot experiment with the increase of N rate,the paddy yield in RNAi and WT increased at low N rate but decreased at higher N rate,yet,the yield stayed enhanced in OX line.The number of panicles increased in all three lines,and the number of spikelets per panicle increased at low N rate but reduced at higher N rate;With the increase of TAL expression level,the seed setting rate increased continuously at low N rate(NO,N5).Whereas at higher N rate(N10,N15),alteration of TAL expression decreased seed setting rate;Alteration of TAL expression level reduced the yield and number of panicles,except that they increased in high N rate(N15).Along with the increment in TAL expression level,the number of spikelets per panicle and 1000-grain weight increased.2.Biomass accumulationIn the field experiment,the biomass accumulation at heading and maturity in high-density treatment was greater than that in low-density;Along with the N rate increment,the biomass accumulation at heading and maturity increased in low-density treatment,whereas in high-density they increased at low N rate but reduced at higher N rate.At maturity stage,the biomass accumulation increased along with the expression level of TAL.In the pot experiment,with the increase of N rate,the dry matter weight at heading stage increased at lower N rate but decreased at higher rate,and the dry matter weight at maturity stage stayed increased.At lower N rate(N0,N5),alteration of TAL expression decreased the dry matter weight at heading stage.With the increase of TAL expression,the dry matter weight at the heading stage increased continuously at higher N rate(N10,N15).In growth chamber,the dry matter weight in high CO2 concentration treatment was higher than that in low CO2 treatment;With the increase of N rate,the dry matter weight all showed an increasing trend.The dry matter weight increased along with the TAL expression level.3.Transcriptome analysisThe TAL gene is metabolically involved in the carbon and N process.Alteration in TAL expression led to significant reduction in differentially expressed gene(DEG)number in CO2 and N rate treatments.When the N rate was low and combined with higher CO2 supply,changes of TAL expression had limited effect on the number of DEG.For the genes involved in the pentose phosphate pathway,tillering and phytohormones(GA,CK and IAA),the changes in CO2 concentration brought the most significant effect,followed by the level of N rate,and TAL gene expression level.