Performance,Gene Mapping And Transcriptome Profile Of Brachytic Stem In Soybean

Soybean originated in China,which is one of the most important oil crops in the world.The soybean yield per unit area is relatively low in China,so the high-yield breakthrough is always the main breeding objective and plant type breeding is an effective way to improve yield in soybean.As a specific stem mutant,soybean brachytic stem shows zigzag in the mian stem and short internodes,and can be used to increase soybean lodging resistance under high-yield environment.Some studies indicated that the development of plant stem was regulated by phytohormones including gibberellin,indoleacetic acid,brassinosteroid.Isolation of soybean brachytic stem gene can provide new insight into the genetic mechanism of plant shoot growth.Here,a pair of near isogenic lines names as NIL-1M and NIL-1 W were used to conduct exogous phytohormones spraying tests to reveal the growth response of brachytic stem.Transcriptome analysis of stem tip tissues of the NIL-2 near isogenic lines and fine mapping of sbl gene using F2 populations between parents with brachytic stem and normal stem lines were carried out to identify target gene and reveal the genetic principle for the brachytic stem.The main results were as follows:1.There were significant differences in plant height and pod number per plant between brachytic and normal stem plants by using two sets of NILs and three F2 populations.The average plant height of NIL-1,NIL-2 brachytic stem plants were 40.5 and 23.9 cm,only 41.0%and 33.2%of the normal ones.Different response trends to exogenous hormone treatments between brachytic and normal stem plants were found.The treatment of 20 mg/L GA3 could promote the growth of brachytic stem plants and recover their zigzag internode to normal shape.The average values of plant height main stem node number,pod number per plants in brachytic stem plant were significantly lower than those of normal stem plants in three F2 populations,however,there also were some brachytic stem plants with good agronomic traits for selection in the populations.2.In the eight F2 populations for genetic analysis of brachytic stem,the segregation ratio of normal to brachytic stem in three crosses,M9449XNK-SB1,NG94-156XNKW24 and NG94-156XMNK,fitted an expected 3:1,and the ratio of a cross Wupiqingrenxsb fitted an expected 15:1,indicating the brachytic stem trait might be controlled by two recessive duplicated genes.Sbl xDuanyebing and other three crosses did not fit 3:1 or 15:1 probably due to their genetic background.The sbl gene was located between BARCSOYSSR₁4₁408 and BARCSOYSSR₁4₁424,with a 347 kb physical distance?Gm 14:47553701-47901399?using 103 F2 recessive individuals of NG94-156×MNK,and located between BARCSOYSSR₁4₁408 and BARCSOYSSR₁4₁411,with a 47kb physical distance?Gm14:47553701-47601358?by using 82 F2 recessive individuals of NG94-156×NK-SB1.There were 28 predicted candidate genes in the region,including some transcription factors such as AP2?Glyma14g38610?,bZIP?Glyma14g38460?and TB/POZ?Glyma14g38640?and Glyma14g38610 was identified as a candidate for the brachytic stem trait.3.Transcript differences of shoot tip tissues of NIL-2M and NIL-2 W were detected by using Affymetrix gene chip.Total 644 differentially expressed genes?DEGs?,of which 562 were up-regulated and 82 down-regulated,were detected with the RMV?fold change>2 and P<0.01?modles by screening the total DEGs of NIL-2.Significant levels of GO were calculated by elimGO algorithm,and 44 significant up-GO and 12 significant down-GO were identified.By cluster analysis,pathway and co-expression analyses,several functions related to the brachytic stem development including response to gibberellin stimulus,cell wall multidimensional,cell growth,jasmonic acid signal regulation were identified,and Glyma07g05760,Glyma14g40530,GIyma05g24790 and Glyma02g35210 were screened out as the important regulatory genes of the brachytic stem trait.