Molecular phylogeny, identification and pathogenicity of Rhizopus oryzae associated with root rot of mulberry in India.

AIMS: Root rot caused by a group of fungi is a serious disease in mulberry. This study aims to identify and characterize Rhizopus oryzae and other fungal species associated with root rot of mulberry in India. METHODS AND RESULTS: Rotted root samples were collected from the mulberry gardens from four states of Southern India. The majority of the isolates identified were R. oryzae, and others were saprophytic fungi, less abundant to occasional. Two methods of inoculations were tested to confirm the pathogenicity of the selected isolates and R. oryzae was found to be pathogenic on susceptible mulberry genotypes RC2 and SRDC-1. Multi gene phylogenetic analyses using the internal transcribed spacer region (ITS), actin (ACT) and translation elongation factor 1-α (TEF), identified the isolates as R. oryzae. Additionally, Ovatospora brasiliensis, Amesia nigricolor, Gongronella butleri, Myrmecridium schulzeri, Scedosporium boydii, Graphium euwallacea, Clonostachys rosea andTalaromyces spp. were also identified. CONCLUSION: This study revealed the existence of eleven species of fungi including the first report of R. oryzae and the occurrence of weak pathogens or saprophytes that are associated with the root rot of mulberry in India. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of R. oryzae causing Rhizopus rot of mulberry in India. Moreover, the occurrence of saprophytes associated with root rot of mulberry was identified. Further studies should focus more on the ability of these species to generate secondary metabolites and extracellular lytic enzymes as they are beneficial for the management of root rot disease.

Withanolide E sensitizes renal carcinoma cells to TRAIL-induced apoptosis by increasing cFLIP degradation.

Withanolide E, a steroidal lactone from Physalis peruviana, was found to be highly active for sensitizing renal carcinoma cells and a number of other human cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Withanolide E, the most potent and least toxic of five TRAIL-sensitizing withanolides identified, enhanced death receptor-mediated apoptotic signaling by a rapid decline in the levels of cFLIP proteins. Other mechanisms by which TRAIL sensitizers have been reported to work: generation of reactive oxygen species (ROS), changes in pro-and antiapoptotic protein expression, death receptor upregulation, activation of intrinsic (mitochondrial) apoptotic pathways, ER stress, and proteasomal inhibition proved to be irrelevant to withanolide E activity. Loss of cFLIP proteins was not due to changes in expression, but rather destabilization and/or aggregation, suggesting impairment of chaperone proteins leading to degradation. Indeed, withanolide E treatment altered the stability of a number of HSP90 client proteins, but with greater apparent specificity than the well-known HSP90 inhibitor geldanamycin. As cFLIP has been reported to be an HSP90 client, this provides a potentially novel mechanism for sensitizing cells to TRAIL. Sensitization of human renal carcinoma cells to TRAIL-induced apoptosis by withanolide E and its lack of toxicity were confirmed in animal studies. Owing to its novel activity, withanolide E is a promising reagent for the analysis of mechanisms of TRAIL resistance, for understanding HSP90 function, and for further therapeutic development. In marked contrast to bortezomib, among the best currently available TRAIL sensitizers, withanolide E's more specific mechanism of action suggests minimal toxic side effects.

Photoperiodic induction of ovarian growth and plasma estradiol secretion in a migratory finch, Emberiza melanocephala: involvement of circadian rhythm.

To demonstrate the involvement of circadian rhythm in photoperiodic time measurement, photosensitive female blackheaded buntings were kept under different photoperiodic schedules consisting of 6 h of main photophase coupled with scotophases of various durations. Ovarian mass and circulating plasma estradiol concentration were found to be elevated in cycles of 6L:6D, 6L:36D, 6L:54D and in control 15L:9D groups. But cycles of 6L:18D, 6L:42D and 6L:66D did not stimulate ovarian growth or elevate circulating plasma estradiol concentration. These results are consistent with the Bünning hypothesis according to which a photoperiodic response is elicited as a result of the coincidence of light with the photoinducible phase of an endogenous circadian rhythm. The results thus indicate the involvement of a circadian rhythm of photoinducibility in ovarian growth and estradiol secretion.

Involvement of threshold photoperiod in control of reproductive rhythmicity in migratory blackheaded bunting, Emberiza melanocephala.

To explore the need for minimum threshold photoperiodicity in regulation of metabolic and reproductive activities of a migratory finch, various programmed light-dark (LD) schedules, such as P1 (3L/21D), P2 (6L/18D), P3 (9L/15D), P4 (12L/12D), P5 (15L/9D), P6 (18L/6D), P7 (21L/3D), and P8 (24L/0D), have been used on photosensitive female blackheaded buntings for 42 days. Results indicate that the photoperiodic thresholds of 3 h, 6 h, and 9 h completely failed to have any response on buntings, while threshold photoperiodicities of 12 h, 15 h, 18 h, 21 h, and 24 h had significant effect (P < .001) on body weight, ovarian weight, and circulating plasma estradiol concentration, suggesting the role of the photoperiod as a primary environmental source to regulate various metabolic and reproductive functions. Further, it has been suggested that the threshold photoperiod in this species appears to be of 12 h duration.

Involvement of circadian rhythm in response to ultrashort photoperiods in blackheaded bunting, Emberiza melanocephala.

Groups of photosensitive adult female blackheaded buntings were exposed to various ultrashort days photoperiodic regimes for 60 days in which a fixed 3 h photophase was coupled with dark phases in cycles of 22 to 32 hours duration. One group of buntings was kept in long days (15L:9D) as control. Significant increase in ovarian weight and circulating plasma estradiol concentration was marked in the cycles of 30 h (3L:27D), and 32 h (3L:29D) photoperiodic schedules as well as in control group (15L:9D), whereas there was no response in the cycles of 22 h (3L:19D) and 24 h (3L:21D). It seems that the response to ultrashort day cycles is due to a phase advance or delay in photosensitivity of the response system repeatedly shows coincidence of the external photophase (3 h) with the photoinducible phase of an endogenous circadian rhythm. Therefore, the present result appears to be consistent with Bünning hypothesis suggesting the involvement of an endogenous circadian component in the female blackheaded bunting.

Circadian aspect of photoperiodic time measurement in a female house sparrow, Passer domesticus.

Endogenous circadian rhythms are involved in various photoperiodic responses of birds. Investigations involving the mechanisms of photoperiodic time measurement in birds have been confined mainly to temperate zone species using males exclusively. Due to the paucity of experimental evidence on subtropical birds that have very wide distribution, the present study was performed using subtropical female house sparrows. Photoperiodic sparrows were subjected to various T cycles for 60 days in which a fixed 3-h photophase was combined with scotophase in cycles of 20-30 h duration. Simultaneously, two groups of birds were also exposed to short days (light:dark = 8L:16D) or long days (15L:9D) as controls. Significant ovarian growth was found only in cycles of 3L:17D, 3L:23D, 3L:25D, and 3L:27D as well as in 15L:9D, whereas no positive response was detected in 3L:19D, 3L:21D, and 8L:16D. Plasma levels of estradiol showed a close relation to ovarian growth. The results indicate that photoperiodic time measurement in house sparrows involves an endogenous circadian rhythm.

Endogenous circadian rhythm in the photoperiodic ovarian response of the subtropical sparrow, Passer domesticus.

Groups of photosensitive female house sparrows have been kept under night-interruption and intermittent light cycles for a period of 6 weeks. The night-interruption cycle consisted of a basic photophase of 6 h and 1 h photointerruption of the dark phase in the 24 h cycle at different points. Ovarian growth was stimulated under cycles in which photointerruption of the dark phase was made 10 h after the onset of basic photophase. The intermittent light cycles consisted of 2 L:2 D, 3 L:3 D, 4 L:4 D, 8 L:8 D and 12 L:12 D besides two control groups held on 7 L:17 D and 17 L:7 D. Ovarian response was observed only in 2 L:2 D, 3 L:3 D, 4 L:4 D, 12 L:12 D and 17 L:7 D cycles. The results of both the experiments are consistent with an avian external coincidence model and indicate that circadian rhythmicity is involved during the initiation of the female avian reproductive system.

Photorefractoriness and its termination in the subtropical house sparrow, Passer domesticus: involvement of circadian rhythm.

Groups of photorefractory female subtropical house sparrows, Passer domesticus, when treated with 6 weeks of a short photocycle (8L:16D) showed significant ovarian growth on their return to a long photocycle (15L:9D). A 6-hr photophase coupled with scotophase of varying durations does not terminate the refractory period under photoperiod cycles of 12 (6L:6D), 36 (6L:30D) and 60 (6L:54D) hr but the refractory period is terminated by light-dark cycles of 24 (6L:18D), 48 (6L:42D) and 72 (6L:66D) hr. These results are consistent with the Bünning hypothesis of coincidence between endogenous photosensitive rhythmicity and environmental photoperiod timing that an endogenous circadian rhythm is involved in the maintenance and termination of photorefractoriness.

Photoperiodic control of ovarian growth in the subtropical house sparrow, Passer domesticus: evidence of an external coincidence system.

Groups of adult female house sparrows (Passer domesticus) were placed under short days (8L/16D) and continuous darkness (DD) after photostimulation by long days (15L/16D) for either 25 or 40 days and another two groups of photostimulated birds were continued on long day (15L/9D) photoperiod. Two groups of photosensitive birds were subjected to 8L/16D or DD and they treated as controls. The rate of ovarian regression was nearly the same under transfer to 8L/16D or DD. Birds placed under long days maintained ovarian growth and this exclude the possibility of refractoriness. However, the photosensitive birds placed under 8L/16D or DD did not show any ovarian growth. The results of these experiments seem to support Bünning - Pittendrigh external coincidence model.

Involvement of a circadian rhythm in the photoperiodic ovarian response of the yellow-throated sparrow, Gymnorhis xanthocollis.

Groups of the photosensitive female yellow-throated sparrow were placed under various light-dark cycles, in which a fixed ultrashort photophase of 3 h was combined with dark phases of varying duration, resulting in cycles of 18-30 h. Simultaneously, two groups of birds, one in short days (8L/16D) and the other in long days (15L/9D), were kept as controls. Significant ovarian growth, observed at 30 and 60 days, was induced by 3 h ultrashort photophase only if it was introduced in the cycles of 18 h (3L/15D), 20 h (3L/17D), 26 h (3L/23D), 28 h (3L/25D) and 30 h (3L/27D) as well as under long days (15L/9D), whereas there was no response to the ultrashort photophase in cycles of 22 h (3L/19D) and 24 h (3L/21D) and in short days (8L/16D). It seems that there is an ovarian response to the ultrashort day cycles when a phase advance or delay of photosensitivity of the response system repeatedly produces coincidence of the external photophase (3 h) with the photosensitive phase of an endogenous circadian rhythm. The results are thus consistent with the Bünning hypothesis, which suggests the involvement of an endogenous circadian rhythm in photoperiodic time measurement.

Photoperiodic ovarian response in yellow-throated sparrow, Gymnorhis xanthocollis: involvement of circadian rhythm.

The experiments aim to investigate the mechanism of photoperiodic time measurement during photoperiodic ovarian response of subtropical yellow-throated sparrow. Groups of the photosensitive female birds were exposed to various night-interruption cycles for a period of 35 days. These light-dark cycles consisted of a basic photophase of 6h and 1h photointerruption of the 18h dark phase in 24h cycle at different points. A control group was also placed under 7L/17D. Ovarian response was observed in the night-interruption cycles in which the photointerruption of dark phase was made 12h after the onset of basic photophase. The results are consistent with the Bünning hypothesis and indicate that an endogenous circadian rhythm is involved in photoperiodic time measurement during initiation of ovarian growth in this species.

Circadian periodicity in yellow-throated sparrow as demonstrated by intermittent light experiments.

Groups of adult photosensitive male yellow-throated sparrows were subjected to different intermittent light cycles viz. 2L/2D, 3L/3D, 4L/4D, 8L/8D and 12L/12D besides two control groups held on 8L/16D and 18L/6D photoperiodic treatments. Testicular growth occurred in 2L/2D, 3L/3D, 4L/4D and 18L/6D but not in 8L/16D, 12L/12D and 8L/16D photoperiodic regimes. The results of this experiment can be interpreted on the basis of circadian rhythm in photosensitivity in an avian external coincidence model. Our findings suggest that multiple light flashes are more effective than a single broad pulse of light of equal duration.

Effects of exogenous prolactin on ovarian growth and fattening in the redheaded bunting, Emberiza bruniceps.

Subcutaneous daily injections of ovine prolactin (PRL) inhibit photoperiodic induction of gonads and fattening in the female redheaded bunting (Emberiza bruniceps). However, birds respond to the same photoperiod (15L:9D) after withdrawal of the exogenous PRL. Further, PRL injections given in late hours during the subjective days induce ovarian regression in the photostimulated females. The results suggest that the PRL has an inhibitory role on gonadal photoperiodic responses in redheaded buntings, and extend our understanding of the regulatory function of PRL in migratory birds.

The photo-gonadal response of a migratory bunting: evidence of an external coincidence system.

Male redheaded buntings (Emberiza bruniceps) were subjected to continuous darkness (DD) or short days (8L/16D) after photo-stimulation (15L/9D) for either 15 or 30 days. Two groups of birds (four each), after photo stimulation for 30 days, were continued on a regimen of 15L/9D. Another two groups (of four each) of photo-sensitive birds were also subjected to DD or 8L/16D; they served as controls. The effect of transfer to DD or 8L/16D on the size of testes was found not the be dependent upon the size attained at the time of transfer. The rate of testicular regression was nearly the same under both the treatments, i.e., in those birds transferred either to DD or to 8L/16D. The birds that were maintained on 15L/9D maintained enlarged testes; this excluded the possibility of the onset of photo-refractoriness during the treatment period. On the other hand, testes were not photo-stimulated in the photo-sensitive birds subjected to DD or 8L/16D. These results are consistent with the Bünning-Pittendrigh avian external coincidence model, but could be explained alternatively by a relatively simple internal coincidence model. Nevertheless, the application of the law of parsimony suggests the acceptance of the hypothesis of the external coincidence model.