Development of randomly amplified polymorphic DNA-sequence characterized amplified region marker for identification of Apocynum venetum LINN. from A. pictum SCHRENK.

Apocynum venetum LINN. is an important Chinese crude drug, and its sibling species A. pictum SCHRENK is a confusable herb which is similar to it. The purpose of this study is to develop DNA molecular markers to distinguish A. venetum from A. pictum through the combinative technologies of bulked segregate analysis (BSA) and randomly amplified polymorphic DNA (RAPD). Two putative markers B08-407 and B03-1368 specific for A. venetum were identified and sequenced. Based on the sequence information, two pairs of primers were designed and synthesized for sequence characterized amplified region (SCAR) markers. But only one primer pair, B03-1368, produced a clear SCAR band in all samples of A. venetum and not in A. pictum. This SCAR marker was found useful for rapid identification of A. venetum from A. pictum.

Restoration of mature etiolated cucumber hypocotyl cell wall susceptibility to expansin by pretreatment with fungal pectinases and EGTA in vitro.

Mature plant cell walls lose their ability to expand and become unresponsive to expansin. This phenomenon is believed to be due to cross-linking of hemicellulose, pectin, or phenolic groups in the wall. By screening various hydrolytic enzymes, we found that pretreatment of nongrowing, heat-inactivated, basal cucumber (Cucumis sativus) hypocotyls with pectin lyase (Pel1) from Aspergillus japonicus could restore reconstituted exogenous expansin-induced extension in mature cell walls in vitro. Recombinant pectate lyase A (PelA) and polygalacturonase (PG) from Aspergillus spp. exhibited similar capacity to Pel1. Pel1, PelA, and PG also enhanced the reconstituted expansin-induced extension of the apical (elongating) segments of cucumber hypocotyls. However, the effective concentrations of PelA and PG for enhancing the reconstituted expansin-induced extension were greater in the apical segments than in the basal segments, whereas Pel1 behaved in the opposite manner. These data are consistent with distribution of more methyl-esterified pectin in cell walls of the apical segments and less esterified pectin in the basal segments. Associated with the degree of esterification of pectin, more calcium was found in cell walls of basal segments compared to apical segments. Pretreatment of the calcium chelator EGTA could also restore mature cell walls' susceptibility to expansin by removing calcium from mature cell walls. Because recombinant pectinases do not hydrolyze other wall polysaccharides, and endoglucanase, xylanase, and protease cannot restore the mature wall's extensibility, we can conclude that the pectin network, especially calcium-pectate bridges, may be the primary factor that determines cucumber hypocotyl mature cell walls' unresponsiveness to expansin.

[The inhibitory effect of Hydrilla verticillata culture water on Microcystic aeruginosa and its mechanism].

This paper studied on the effect and mechanism that the growth of M. aerugonsa was markedly inhibited by the H. verticillata culture water. During treatment, the photosynthetic rate of M. aerugonsa declined, while its respiratory rate and SOD activity increased firstly, then decreased as the treatment went on. Its membrane permeability also increased significantly. TEM photographs showed that the ultrastructure of cell membrane, thylakoid lamella and pith nucleoid of M. aerugonsa were destroyed severely. Inhibitory effects could be observed only when the extracts were extracted by ether. The more extracts from ether, the better inhibitory effect observed. It suggested that the inhibitory effects of H. verticillata on M. aeruginosa were through excreting substances into water. GC/MS analytic result showed that the ether extract mainly consisted of 1,2-benzenedicarboxylic acid diisooctyl ester, dibutyl phthalate, and 1,2-benzenedicarboxylic acid butyl 2-methylpropyl ester.