The influence of kinetin on tobacco ringspot virus infectivity and the effect of virus infection on the cytokinin activity in intact leaves of Nicotiana glutinosa L

Current understanding of the interplays between host hormones and plant viral infections

Phytohormones mediate plant development and responses to stresses caused by biotic agents or abiotic factors. The functions of phytohormones in responses to viral infection have been intensively studied, and the emerging picture of complex mechanisms provides insights into the roles that phytohormones play in defense regulation as a whole. These hormone signaling pathways are not simple linear or isolated cascades, but exhibit crosstalk with each other. Here, we summarized the current understanding of recent advances for the classical defense hormones salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) and also the roles of abscisic acid (ABA), auxin, gibberellic acid (GA), cytokinins (CKs), and brassinosteroids (BRs) in modulating plant–virus interactions.

Effect of virus infection on the secondary metabolite production and phytohormone biosynthesis in plants

Plants have evolved according to their environmental conditions and continuously interact with different biological entities. These interactions induce many positive and negative effects on plant metabolism. Many viruses also associate with various plant species and alter their metabolism. Further, virus-plant interaction also alters the expression of many plant hormones. To overcome the biotic stress imposed by the virus's infestation, plants produce different kinds of secondary metabolites that play a significant role in plant defense against the viral infection. In this review, we briefly highlight the mechanism of virus infection, their influence on the plant secondary metabolites and phytohormone biosynthesis in response to the virus-plant interactions.

Influence of white clover mosaic potexvirus infection on the endogenous cytokinin content of bean

The cytokinin content in the primary leaves of bean (Phaseolus vulgaris) was monitored for 10 d after inoculation with white clover mosaic potexvirus. The cytokinins were isolated, purified, separated by high-performance liquid chromatography, and quantified by radioimmunoassay. The cytokinins detected at the time of inoculation (d 0) were: (a) the free bases, zeatin (Z), dihydrozeatin (DZ), and isopentenyladenine; (b) the riboside, DZ riboside (DZR); (c) the O-glucosides of DZ, DZR, and Z riboside; (d) the nucleotides, Z riboside-5'-monophosphate and isopentenyladenosine-5'-monophosphate; and (e) trace amounts of Z-9-glucoside and DZ-9-glucoside. During the 10 d after inoculation with white clover mosaic potexvirus, marked quantitative changes in this cytokinin profile were observed. The concentration of the free bases and DZR decreased, accompanied by an increase in the 9-glucosides and the nucleotides. Virus titer increased rapidly 3 d after inoculation, attaining a maximum level at d 5. This increase coincided with the increases in the 9-glucosides and the nucleotides. We propose that the decline in the cytokinin free bases and riboside may allow the increase of virus titer in bean and lead to the senescence of infected leaves.

Cytoplasmic male sterility in barley : 12. Associations between disease resistance and restoration of msm1 fertility in the wild progenitor of barley

The associations between seedling reactions to three fungal pathogens (Puccinia hordei, Pyrenophora teres, and Rhynchosporium secalis) or between adult plant reaction to Rh. secalis and the male fertility restoration ability of msml cytoplasm were studied in about 100 accessions of Hordeum spontaneum. Significant differences in the severity of infection between classes of restoration ability were observed with two cultures of P. hordei (751 and 7,649) and with Rh. secalis on adult plants in the field. The cultures 7,432, 751 and 7,649 of P. hordei showed significant positive correlations between infection severity and restoration percentage. The culture 7,620 of P. hordei displayed a significant negative correlation. Rh. secalis (cultures 492A and 531 combined) on seedlings and the natural field infection in the 1978 season showed significant positive correlations. The accession class with the partial restoration ability of 0.1 to 5.0% of the four arbitrary classes (0.0, 0.1-5.0, 5.1-55.0, and 90.1-100%), displayed the lowest mean severity of infection in six of the eleven tests. Some frequently appearing races of these pathogens may operate as selective agents in the maintenance of restoration ability in the original spontaneum populations.