| QB205-1-3-3 and its wild type,although the values were slightly higher in the transgenic line.6.Total soluble sugar content was increased more than 4 times in the flag leaves of both HB123-1-Wheat(Triticum aestivum L.)is the major food crop in the world.With the fast-increasing human population,it is crucially important to maximize yield of crops including wheat.A major determinant of grain yield is the grain weight which is positively correlated with grain size including grain length and grain width.Previous work in our lab has identified ABP7 as a G-box binding b HLH transcription activator whose over-expression led to increased seed size and weight in both Arabidopsis and maize transgenic plants.In an effort to create new wheat varieties aiming at increasing grain yield,constructs expression ABP7 were made in the lab and introduced into wheat by genetic transformation,and T1 seeds of putative transgenic lines were obtained.The objective of this study is to molecularly identify the homozygous transgenic wheat lines expressing ABP7 and to phenotype their growth and development with a focus on the yield-related traits such as grain size,number and weight.To achieve this,putative transgenic lines with their respective wild type controls grown in green house as well as in field condition were screened by immunostrips,PCR,Southern blotting and q PCR,and morphologically phenotyped in 2018 and 2019,and physiologically analyzed.The results obtained are as follows:1.Homozygous transgenic wheat lines were obtained by immunostrips and PCR analyses,namely HB123-1-3-2,HB123-3-6-3 and HB123-5-10-8(expressing PABP7-ABP7 in CB037 genetic background);HB287-2-18-14,HB287-5-27-9 and HB287-15-25-6(expressing Pubi-ABP7 in Fielder background);QB205-1-3-3,QB205-3-13-5 and QB205-5-14-3(expressing PABP7-ABP7 in Fielder background).2.Southern blotting results confirmed the integration of ABP7 into the genome of transgenic wheat lines and indicated that both HB123-1-3-2 and HB287-15-25-6 harbor more than one copies of ABP7 in the genome while QB205-1-3-3 is a transgenic event with a single copy insertion.3.Quantitative PCR analysis revealed that the transcript level of ABP7 was significantly(p<0.05)enhanced in transgenic lines HB123-1-3-2 and HB287-15-25-6 as compared to their corresponding wild-type plants CB037 or Fielder.The expression of ABP7 showed no significant(p<0.05)increase in QB205-1-3-3 comparing to its wild-type control.4.Grain traits including grain number per panicle,thousand-grain weight,grain weight per panicle,grain length,and grain width were significantly(p<0.05)increased in both HB123-1-3-2 and HB287-15-25-6 transgenic lines comparing to wild type CB-037 or Fielder.These phenotypes(except the grain number per panicle in HB287-15-25-6)were repeatedly detected in the two transgenic lines in both the winter season of 2018 and the summer season of 2019.For transgenic line QB205-1-3-3,trait parameters including grain number per panicle,thousand-grain weight,grain weight per panicle,and grain width were significantly(p<0.05)increased in transgenic(T3)comparing to that of wild type in the winter season of 2018.However,all the traits tested for this line at T4 showed no significant difference(p<0.05)with that in its wild type Fielder in the summer season of 2019,although the values of most of the traits were slightly higher in transgenic plants than that in wild type control.5.Total chlorophyll,chlorophyll a and chlorophyll b were all significantly(p<0.05)increased in the flag leaves of both HB123-1-3-2 and HB287-15-25-6 transgenic lines as compared to that in wild type plants.No significant difference(p<0.05)in chlorophyll was observed between transgenic line 3-2and HB287-15-25-6 transgenic lines as compared to wild type control.In transgenic line QB205-1-3-3,total soluble sugar content was also significantly(p<0.05))increased,but to a less extent than that in HB123-1-3-2 and HB287-15-25-6.These data indicate that homozygous ABP7-expressing transgenic wheat lines with significantly improved yield-related traits have been created,providing valuable germplasm resources for wheat yield enhancement. |
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