Transcriptome Analysis Of Maize Photoperiod-insensitive Near-isogenic

Maize(Zea mays ssp.mays L.),as one of the most widespread food crops in the world,recently has been the first place in the planting area beyond that in wheat and rice in our country.To find more and new cultivar,tropical and subtropical maize were discovered with the abundant of genetic variation,but photoperiod sensitivity of these materials will be the major obstacle in temperate regions.Studying on photoperiod mechanism has been reported previously,but how these genes in this pathway activated the floral development in maize,is still not clear.Plant photoperiod is extremely complex,involving multiple genes coordinate participation,in this study we indicated that two materials,including photoperiod-insensitivity materials Huangzao4 and the near-isogenic lines 496-10(H4-NIL)obtained from a crossing of Huangzao4 and tropical photoperiod-sensitivity CML288,showed different expression pattern and regulation mechanism in different development stage((vegetative stage,vegetative growth to reproductive growth conversion period,reproductive stage)under long day condition by RNA sequencing,bioinformatics analysis and RT-PCR validation.The main conclusions are as follows:1.Through the shoot apex morphology(SAM)observation,we found that compared with HZ4-NIL,the SAM shapes of HZ4 were the same in the 3-leaf period,but present one leaf period earlier from the 4-to 7-leaf stages.These results showed that the floral transition occurred one leaf period earlier in HZ4 than HZ4-NIL.According to the stem tip shape,we defined three developmental periods,vegetative period;Vegetative growth to reproductive growth period;Reproductive stage.Using RNA-seq technology from H4 and H4-NIL in these three leaf stages we have analyzed 25 ~ 28 million total reads and about 64% of the reads has a unique matching sites on the genome.2.Bioinformatics analysis showed that the H4 and H4-NIL corresponding leaf stage respectively 357,531,736 and 531 differentially expressed genes.For those upregulated genes in HZ4-NIL compared to HZ4,there were 99,126,94 and 203 genes specifically expressed in four different leaf stages,independently,of which four genes were raised throughout the four leaf stages;while for those decreased genes,there were 122,279,417 and 229 genes specifically expressed in four different leaf stage,and 12 genes were downregulated during these four leaf stage.According to the GO annotation,the enrichment of gene function mainly focused on the catalytic activity,REDOX enzyme activity,metabolic process and REDOX reaction.In the biological process category,these differences mainly involved in ion transport and photosynthesis genes,and the biological process and KEGG pathway network combined with different expression genes was constructed by the Cytoscape(v3.0.2)plugin Clue GO + Cluepedia v2.1.3,finally we found differentially expressed genes involved more than one function category,which indicated photoperiod pathway was involved in a variety of functional genes,a variety of metabolic regulation and control of a very complex process and may have a closely relative connection with other mechanisms regulation.3.By clustering of different expression genes in different period,these genes were divided into three categories: the first category is likely to play a main role in the transition stage of vegetative growth to reproductive growth phase;The second category of genes may be more involved in the regulation of vegetative growth;The third class may be related to reproductive growth stage of growth and development regulation.4.19 genes related to photoperiod were selected from the H4 and H4-NIL,and were clustered into three expression categories: the first kind of gene GRMZM2G002220,GRMZM2G013398,GRMZM2G076602,GRMZM2G138750,GRMZM2G016756,raised in the vegetative growth and reproductive growth stage,cut in vegetative growth to convert phase;The second AC233888.1_FG002,GRMZM2G062541,GRMZM2G156692,GRMZM2G449950,GRMZM2G021777,GRMZM2G092363,GRMZM2G162737,GRMZM2G165488,raised in vegetative growth to reproductive growth stage,the vegetative growth and reproductive growth stage;The third kind GRMZM2G175265,GRMZM2G474769,GRMZM2G004483,GRMZM2G014902,GRMZM2G138455,GRMZM2G165042,raised at vegetative stage,in the vegetative growth to reproductive growth stage and reproductive stage.5.Through digging up the relationship between these photoperiod related genes by the expression patter,we supposed that higher expression CCA1 / LHY,TOE3 and COL9 may cause decreasing of CO expression and lead to the delayed blooming in HZ-NIL.In addition,we also found that these photoperiod sensitive differentially expressed genes involved in seed germination,seedling growth,and also respond to abiotic stress,etc.