The CONSTANS (CO) family is an important regulator of flowering in photoperiod sensitive plants. But information regarding their role in day neutral plants is limited. We report identification of nine Group I type CONSTANS-like (COL) genes of banana and their characterization for their age dependent, diurnal and tissue-specific expression. Our studies show that the Group I genes are conserved in structure to members in other plants. Expression of these genes shows a distinct circadian regulation with a peak during light period. Developmental stage specific expression reveals high level transcript accumulation of two genes, MaCOL3a and MaCOL3b, well before flowering and until the initiation of flowering. A decrease in their transcript levels after initiation of flowering is followed by an increase in transcription of other members that coincides with the continued development of the inflorescence and fruiting. CO binding cis-elements are observed in at least three FT-like genes in banana suggesting possible CO-FT interactions that might regulate flowering. Distinct tissue specific expression patterns are observed for different family members in mature leaves, apical inflorescence, bracts, fruit skin and fruit pulp suggesting possible roles other than flowering. This is the first exhaustive study of the COL genes belonging to Group I of banana.
FLOWERING LOCUS T (FT) and TERMINAL FLOWER1/CENTRORADIALIS (TFL1/CEN) are the key regulators of flowering time in plants with FT promoting flowering and TFL1 repressing flowering. TFL1 also controls floral meristem identity and its maintenance. In this study we have characterized two pomegranate (Punica granatum L.) TFL1/CEN-like genes designated as PgTFL1 and PgCENa. The expression of PgTFL1 and PgCENa fluctuated through alternate pruning and flowering cycles, being highly expressed during the vegetative phase (immediately after pruning) and decreasing gradually in the months thereafter such that their lowest levels, especially for PgCENa coincided with the flowering phase. Both the genes are able to functionally suppress the Arabidopsis tfl1-14 mutant flowering defect. Their expression in Arabidopsis resulted in delayed flowering time, increased plant height and leaf number, branches and shoot buds as compared with wild type, suggesting that PgTFL1 and PgCENa are bonafide homologs of TFL1. However, both the genes show distinct expression patterns, being expressed differentially in vegetative shoot apex and floral bud samples. While PgTFL1 expression was low in vegetative shoot apex and high in flower bud, PgCENa expression showed the opposite trend. These results suggest that the two TFL1s in pomegranate may be utilized to control distinct developmental processes, namely repression of flowering by PgCENa and development and growth of the reproductive tissues by PgTFL1 via distinct temporal and developmental regulation of their expression.
A semi-purified extract of low-altitude Podophyllum hexandrum (REC-2001) containing a relatively low content of podophyllotoxin (3.25 %) exhibited potent antioxidant ability in lipid media (at 1000 microg/mLagainst 0.25 kGy) and significant (p < 0.05) hydroxyl ion scavenging potential (78.83 % at 500 microg/mL). In vitro investigations revealed the ability of REC-2001 to significantly (p < 0.05) reduce radiation-induced hemolysis (2 microg/mL; 46.184 %) and nitric oxide scavenging levels (IC (50): 792 +/- 1.25 microg/mL). Protection of the hemopoietic system of Strain 'A' mice administered 20 mg/kg BW REC-2001 30 min prior to lethal irradiation (10 Gy) was recorded and was mediated by free radical scavenging and lowering of lipid oxidation. Further studies investigating the effects of REC-2001 on stem cell modulation are warranted.
Banana is an important day neutral food crop with a long flowering/fruiting cycle that is affected by hot summers or cold winters in different places. Manipulating its life cycle requires an understanding of its flowering time machinery to bypass these stresses. Twelve FLOWERING LOCUS T (FT) and two TWIN SISTER OF FT (TSF) members were isolated from banana and their organization and expression pattern studied during development in two varieties that differ in flowering time namely Grand Nain (AAA genotype) and Hill banana (AAB genotype). The expression of at least 3 genes namely MaFT1, MaFT2 and MaFT5 (and to some extent MaFT7) increases just prior to initiation of flowering. These four genes and five others (MaFT3, MaFT4, MaFT8, MaFT12 and MaTSF1 could suppress the delayed flowering defect in the Arabidopsis ft-10 mutant and induce early flowering upon over-expression in the Col-0 ecotype. Most genes are diurnally regulated and differentially expressed during development and in various vegetative and reproductive tissues suggesting roles besides flowering. Subtle amino acid changes in these FT/TSF-like proteins provide interesting insights into the structure/function relationships of banana FTs vis-à-vis Arabidopsis. The studies provide a means for manipulation of flowering in banana for better management of resources and to reduce losses through abiotic stresses.
With an aim to enhance low temperature impact strength, blends of PP-cp (Impact Grade PP) and metallocene-catalyzed plastomer (EXACT® ethylene-α-octene copolymer) were prepared using a co-rotating, intermeshing twin-screw extruder in 90 : 10, 80 : 20, 70 : 30, and 60 : 40 weight ratio. Rheological properties studied by Haake’ single-screw extruder with torque rheometer attachment and capillary die showed pseudoplastic melt behavior at 220°C in the shear rate range of 400—4000 s—1. Density and MFI determinations showed minimal change. Morphology studied by low voltage scanning electron microscope (LVSEM) of blend samples showed distinct biphasic blend morphology wherein PP-cp as continuous phase and plastomer as spherical domains (0.5—2 μm size) with stabilized distribution and dispersion. Izod impact strength of the blends at varied temperatures (23, 0, -10, -20, -30, and -40°C) showed substantial enhancement in low temperature impact strength compared to the base polymer (from 44 J/m in case of pure PP-cp to 539 J/m in case of 40% plastomer blend at -40°C).
In tropics, combined stresses of drought and heat often reduce crop productivity in plants like Musa acuminata L. We compared responses of two contrasting banana genotypes, namely the drought-sensitive Grand Nain (GN; AAA genome) and drought tolerant Hill banana (HB; AAB genome) to individual drought, heat and their combination under controlled and field conditions. Drought and combined drought and heat treatments caused greater reduction in leaf relative water content and greater increase in ion leakage and H O content in GN plants, especially in early stages, while the responses were more pronounced in HB at later stages. A combination of drought and heat increased the severity of responses. Real-time expression patterns of the A-1 and A-2 group DEHYDRATION-RESPONSIVE ELEMENT BINDING (DREB) genes revealed greater changes in expression in leaves of HB plants for both the individual stresses under controlled conditions compared to GN plants. A combination of heat and drought, however, activated most DREB genes in GN but surprisingly suppressed their expression in HB in controlled and field conditions. Its response seems correlated to a better stomatal control over transpiration in HB and a DREB-independent pathway for the more severe combined stresses unlike in GN. Most of the DREB genes had abscisic acid (ABA)-responsive elements in their promoters and were also activated by ABA suggesting at least partial dependence on ABA. This study provides valuable information on physiological and molecular responses of the two genotypes to individual and combined drought and heat stresses.
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