PATERNAL INHERITANCE OF PLASTID DNA IN GENUS PHARBITIS

The inheritance of plastid DNA in Pharbitis was studied by the method of restriction fragment length polymorphisms (RFLP).Experimental results showed that plastid DNA from Pharbitis was paternally inherited in reciprocal crosses,P. nil ×P. limbata and P. limbata×P. nil hybrids.But,in the cross of P. limbata×P. nil,the possibility of biparental inheritance of plastid DNA could not be roled out in our preliminary experiment.Thus Pharbitis became the third genus among angiosperms characterized with male plastid transmission.The mechanisms of paternal plastids DNA inheritance in Pharbitis is unclear.The authors proposed that dilution,exclusion and/or degeneration of maternal plastid,including their DNA,after fertilization should be considered.

Research on the Mutants of Pharbitis nil

[Objective]The research aimed at investigating mechanisms of the changes of pharbitis.nil flower colors and leaf colors.[Method]The recombinant plasmid pMD18-T/Tpn was constructed by amplifying the target fragments from young leaf tissues of the blue and white mutant of Pharbitis nil with PCR technology and investigating in the fields.[Result]The results of investigations in the fields suggested that the mutant was segregated in F3 generation,and the mutations of leaf colors did not affect the changes of flower colors.The results of PCR amplification showed that there was a band about 330 bp in genomic DNA of Lanbai,Chunlan,Dahua,respectively,however,no bands were found in genomic DNA of Chunguang,Baixue,Ping＇anhong and Chuiman.[Conclusion]The sequence of recombinant plasmid of the mutant was indeed a fragment of the transposon of Pharbitis nil.

Stress-Induced Flowering in Pharbitis—A Review

Many plant species are induced to flower by stress. Stress-induced flowering has been studied mostly in the short-day plant pharbitis (also called Japanese morning glory;Ipomoea nil, formerly Pharbitis nil). In this article, physiological characteristics, the regulation by salicylic acid (SA) and the expression of flowering-related genes in stress-induced flowering in pharbitis are reviewed. Pharbitis flowered under long-days in response to poor nutrition or low temperature. The pharbitis plants induced to flower by stress reached anthesis, fruited and produced fertile seeds. The progeny of the stressed plants developed normally. Grafting experiments indicated that a transmissible flowering stimulus is involved in poor nutrition stress-induced flowering. Aminooxyacetic acid (AOA), a phenylalanine ammonia-lyase (PAL) inhibitor, inhibited the stress-induced flowering, and this inhibition was overcome by SA. Stress induced PAL activity and SA biosynthesis. PnFT2, a pharbitis ortholog of the flowering gene FLOWERING LOCUS T of Arabidopsis thaliana, was expressed when the plants were induced to flower by stress. The overexpression of PnFT2 induced flowering, and PnFT2RNAi inhibited it. AOA inhibited PnFT2 expression induced by stress, and SA eliminated this inhibitory effect. SA enhanced PnFT2 expression under poor nutrition but not under non-stressful conditions. Therefore, stress may induce the production of SA and other unknown factor(s) that may work in combination to induce PnFT2 expression and flowering.

SPECIFIC PROTEIN OCCURRENCE RELATED WITH PHOTOPERIODIC FLOWER INDUCTION IN THE COTYLEDONS OF Pharbitis nil CV. VIOLET

In our experiment, three groups of seedlings of SDP Pharbitis nil cv. violet were sepa-rately treated with three different photoperiods (1,16 h dark period--SD; 2, continuous illumi-nation--CL; 3, 16 h dark treatment with 10 min white light in the middle of the dark period--NB). By analysing proteins in the cotyledons from three groups with 2-D PAGE, we found nodifference in protein pattern between the three groups at 0 or 8 h after photoperiodic treatments.At 24 h after the treatments, a specific protein(MW:19 kD; pI: 4.5)appeared only in the cotyledonsof the seedlings which endured SD. This protein disappeared at 72 h after SD. ActinomycinD could inhibit flowering and the specific protein occurrence when applied to cotyledonsprior to SD, but it had no inhibition effect on flowering as well as the specific proteinoccurrence when applied to cotyledons after SD. Chloroamphenicol, a protein synthesisinhibitor, inhibited flowering when applied to cotyledons prior to or immediately after SD,but it did not inhibit flowering when applied to cotyledons at 24 h after SD. With the jointconsideration of the effects of defoliation and inhibitor applications on flowering, wededuced that the 19 kD protein occurrence correlated with the commitment to flowering. Thegene transcription related with induction was fulfilled within the SD period, while thespecific protein synthesis lasted 24 h after SD. The key regulation step of biochemical changesduring induction was at the transcriptional level.