The Screening And Identification Of Photoperiod-sensitive Genes Which Relate To Microtuber Formation

Potato (Solanum tuberosum L.) is the fourth most important food crop in the world. Tuber is the major economical organ of potato, so it is significant to study tuber development for increasing potato output and improving potato quality. Fluctuations in day length are critical to promote differentiation of tuber in potato, and evidence has been obtained that the underground stolons are induced tuber development under short days (SDs), while not under long days(LDs). Microtuber, which is produced by potato plantlet cultivated in artificial medium, is the same as conventional tuber in organization structure, growth and development, genetic stability, so it provides an easier experiment model. In this research, we analyzed the transcript levels of25candidate genes in SDs and LDs, respectively, and found3of them are rhythmic. Via transgene technology, we can know the influence of these three genes on tuberization, further more to identify the molecular mechanisms on tuber formation. The main results are as follows.1) According to the transcript levels of25candidate genes in LDs and SDs,8genes are identified to have differential expression. By verifying expression fluctuations of the8genes in2days under LDs and SDs respectively,3of them seem to be rhythmic and are picked out. According to the annotated functions in PGSC, the3genes are named as StPIF3(PGSC0003DMT400041156), StGI (PGSC0003DMT400048370), StTOCl (PGSC0003DMT400050252), respectively.2) Expression patterns of the3genes are different among three genotype potato E20, E26, E109. As E26is photoperiod-sensitive, it forms microtubers only under SDs. On the contrast, E20and E109are photoperiod-independent—E20cannot form tubers under neither SDs nor LDs, while E109can form tubers under both LDs and SDs. The expression patterns reveal that, StPIF3functions as signal transduction, StGI responds to light, and StTOCl is in charge of circadian clock.3) Sequence homology of each gene in E20, E26and E109is as high as97%, which suggests that the functions of3genes are conservative and are critical to potato plant. 4) In StPIF3interference lines, transcript level of StGI gene is lowered, as is StCO gene, however StSP6A gene transcript level increases heavily. It indicates that StPIF3is able to influence the transcriptions of StGI, StCO, StSP6A. As StSP6A protein promotes tuberization, we drew the conclusion that StPIF3inhibits tuber formation.