KINETIC INDUCTION OF OAT SHOOT PULVINUS INVERTASE MESSENGER-RNA BY GRAVISTIMULATION AND PARTIAL CDNA CLONING BY THE POLYMERASE CHAIN-REACTION

An asymmetric (top vs. bottom halves of pulvini) induction of invertas e mRNA by gravistimulation was analyzed in oat shoot pulvini. Total RN A and poly(A)+ RNA, 'solated from oat pulvini, and two oligonucleotide primers, corresponding to two conserved amino acid sequences (NDPNG a nd WECPD) found in invertase from other species, were used for the pol ymerase chain reaction (PCR). A partial length cDNA (550 bp) was obtai ned and characterized. A 62% nucleotide sequence homology and 58% dedu ced amino acid sequence homology, as compared to beta-fructosidase of carrot cell wall, was found. Northern blot analysis showed that there was an obviously transient induction of invertase mRNA by gravistimula tion in the oat pulvinus system. The mRNA was rapidly induced to a max imum level at 1 h after gravistimulation treatment and gradually decre ased afterwards. The mRNA level in the bottom half of the oat pulvinus was significantly higher than that in the top half of the pulvinus ti ssue. The kinetic induction of invertase mRNA was consistent with the transient accumulation of invertase activity during the graviresponse of the pulvinus. This indicates that the expression of the invertase g ene(s) could be regulated by gravistimulation at the transcriptional l evel. Southern blot analysis showed that there were two to three genom ic DNA fragments which hybridized with the partial-length invertase cD NA.