Comprehensive studies reveal physiological and genetic diversity in traditional rice cultivars for UV-B sensitivity.

Acclimation to crop niches for thousands of years has made indigenous rice cultivars better suited for stress-prone environments. Still, their response to UV-B resiliency is unknown. 38 rice landraces were grown in cemented pots in a randomised block design with three replicates under open field conditions in Sambalpur University in the wet season of 2022. Half of the plants in each of the cultivars were administered UV-B radiation at the panicle emergence stage in an adjustable UV-B chamber permitting sunlight, and the effects of the stress on various morpho-physiological features, such as spikelet sterility, flag leaf photosynthetic and flavonoid pigment contents, and lipid peroxidation activities, were estimated for calibration of stress resistance. The experiment identified Swarnaprabha and Lalkain as the most sensitive and resilient to stress respectively, and the differential response between them was further revealed in the expression of genes related to UV-B sensitivity. Subject to the stress, Swarnaprabha exhibited symptoms of injuries, like leaf burns, and a higher loss of various photosynthetic parameters, such as pigment contents, SPAD and Fv/Fm, ETR and qP values, while NPQ increased only in Lalkain. Exposure to UV-B increased the total phenolic and flavonoid contents in Lalkain while depressing them in Swarnaprabha. Such an effect amounted to a higher release of fluorescent energy in the latter. The levels of expression of gene families controlling flavonoid activation and UV-B signal transduction, such as OsWRKY, OsUGT, OsRLCK, OsBZIP, OsGLP, and CPD photolyase were similar in both the cultivars in the control condition. However, exposure to UV-B stress overexpressed them in resilient cultivars only. The magnitude of expression of the genes and the impact of the stress on photosynthetic parameters, phenolic compounds and pubescent hair structure at the panicle emergence stage could be valid indicators among indigenous rice for UV-B tolerance.

MicroRNAs modulate ethylene induced retrograde signal for rice endosperm starch biosynthesis by default expression of transcriptome.

Control of stage specific spike in ethylene production at anthesis has been a vauable route to potentially enhance genetic ceiling for grain filling of rice spikelet. A number of genes controlling ethylene homeostasis and starch synthesis have been identified so long, but lack of credible information on master modulation of gene expression by miRNAs and their target genes associated with hormonal dynamics obfuscate mechanisms controlling genotype difference in quantum of grain filling. The confusion accounts for consequent shrinkage of options for yield manipulation. In a two by two factorial design, miRNA regulation of spikelet specific grain development in low against high sterile recombinant inbred lines of rice Oryza sativa L. namely CR 3856-62-11-3-1-1-1-1-1-1 (SR 157) and CR 3856-63-1-1-1-1-1-1-1 (SR 159) respectively, and inferior verses superior spikelets were compared during first 10 days after anthesis. Grain filling was poorer in SR159 than SR157 and inferior spikelets in the former were most vulnerable. Between the cultivars, overall expression of unique miRNAs with targets on ethylene pathway genes was higher in SR159 than SR157 and the situation was opposite for auxin pathway genes. Precision analysis in psTarget server database identified up-regulation of MIR2877 and MIR530-5p having Os11t0141000-02 and Os07t0239400-01 (PP2A regulatory subunit-like protein and ethylene-responsive small GTP-binding proteins) and MIR396h having Os01t0643300-02 (an auxin efflux carrier protein) and Os01t0643300-01 (a PIN1-like auxin transport protein), as targets with highest probability at anthesis and 5 days after anthesis respectively, in the inferior spikelet and the fold change values of DGE matched with pattern of gene expression (relative transcript level) in the qRT-PCR studies conducted for relevant miRNAs and protein factors for ethylene and auxin signalling. In conclusion, epigenetic regulation of both auxin and ethylene homeostasis control grain filling of rice spikelet was established, but evidences were more robust for the latter.

Controlling the trade-off between spikelet number and grain filling: the hierarchy of starch synthesis in spikelets of rice panicle in relation to hormone dynamics.

The advent of dwarf statured rice varieties enabled a major breakthrough in yield and production, but raising the ceiling of genetically determined yield potential even further has been the breeding priority. Grain filling is asynchronous in the rice panicle; the inferior spikelets particularly on secondary branches of the basal part do not produce grains of a quality suitable for human consumption. Of the various strategies being considered, the control of ethylene production at anthesis has been a valuable route to potentially enhance genetic yield level of rice. The physiology underlying spikelet development has revealed spikelet position-specific ethylene levels determine the extent of grain filling, with higher levels resulting in ill-developed spikelet embodying poor endosperm starch content. To break the yield barrier, breeders have increased spikelet number per panicle in new large-panicle rice plants. However, the advantage of panicles with numerous spikelets has not resulted in enhanced yield because of poor filling of inferior spikelets. High spikelet number stimulates ethylene production and downgrading of starch synthesis, suggesting a trade-off between spikelet number and grain filling. High ethylene production in inferior spikelets suppresses expression of genes encoding endosperm starch synthesising enzymes. Hence, ethylene could be a retrograde signal that dictates the transcriptome dynamics for the cross talk between spikelet number and grain filling in the rice panicle, so attenuation of its activity may provide a solution to the problem of poor grain filling in large-panicle rice. This physiological linkage that reduces starch biosynthesis of inferior kernels is not genetically constitutive and amenable for modification through chemical, biotechnological, surgical and allelic manipulations. Studies on plant genotypes with different panicle architecture have opened up possibilities of selectively improving starch biosynthesis of inferior spikelets and thereby increasing grain yield through a physiological route.

Corrigendum to: Controlling the trade-off between spikelet number and grain filling: the hierarchy of starch synthesis in spikelets of rice panicle in relation to hormone dynamics.

The advent of dwarf statured rice varieties enabled a major breakthrough in yield and production, but raising the ceiling of genetically determined yield potential even further has been the breeding priority. Grain filling is asynchronous in the rice panicle; the inferior spikelets particularly on secondary branches of the basal part do not produce grains of a quality suitable for human consumption. Of the various strategies being considered, the control of ethylene production at anthesis has been a valuable route to potentially enhance genetic yield level of rice. The physiology underlying spikelet development has revealed spikelet position-specific ethylene levels determine the extent of grain filling, with higher levels resulting in ill-developed spikelet embodying poor endosperm starch content. To break the yield barrier, breeders have increased spikelet number per panicle in new large-panicle rice plants. However, the advantage of panicles with numerous spikelets has not resulted in enhanced yield because of poor filling of inferior spikelets. High spikelet number stimulates ethylene production and downgrading of starch synthesis, suggesting a trade-off between spikelet number and grain filling. High ethylene production in inferior spikelets suppresses expression of genes encoding endosperm starch synthesising enzymes. Hence, ethylene could be a retrograde signal that dictates the transcriptome dynamics for the cross talk between spikelet number and grain filling in the rice panicle, so attenuation of its activity may provide a solution to the problem of poor grain filling in large-panicle rice. This physiological linkage that reduces starch biosynthesis of inferior kernels is not genetically constitutive and amenable for modification through chemical, biotechnological, surgical and allelic manipulations. Studies on plant genotypes with different panicle architecture have opened up possibilities of selectively improving starch biosynthesis of inferior spikelets and thereby increasing grain yield through a physiological route.

Grain density and its impact on grain filling characteristic of rice: mechanistic testing of the concept in genetically related cultivars.

Physiological factors controlling assimilate partitioning was compared in relation to panicle architecture of lax- (Upahar) and compact-panicle (Mahalaxmi) rice cultivars. Grain number and ethylene production at anthesis are low, but filling rate is high in the former compared to high grain number and ethylene production and poor filling trait of the latter. Similar to Mahalaxmi, its progenitors Pankaj and Mahshuri, had attributes of high grain number and grain density, but grain filling was higher and ethylene evolution was lower. Disturbed genetic coherence owing to imbalance of gene groups brought in the cross combinations of Mahshuri and Pankaj could be responsible for high ethylene production leading to semi sterility of Mahalaxmi as the hormone slackened endosperm starch bio-synthesis enzyme activities. Mahalaxmi inherited grain compactness trait of its progenitors, but not the physiological attribute for reduced ethylene production, which impacted grain filling. Upahar, the progeny genotype of Mahalaxmi and IR62 cross, inherited the dominant allele for low ethylene production and good grain filling traits from the high yielding IR62. In conclusion grain filling in compact-panicle rice becomes poor subject to expression of recessive allele for high ethylene production, but the allele is amenable for suppression by corresponding dominant allele in a genetic breeding.

Association of Sp1 and survivin in epithelial ovarian cancer: Sp1 inhibitor and cisplatin, a novel combination for inhibiting epithelial ovarian cancer cell proliferation.

The expression of specificity protein 1 (Sp1) and survivin was evaluated in clinical specimens of epithelial ovarian cancer (EOC) patients. When compared to normal tissue, EOC samples showed high expression of Sp1 and survivin using qPCR (Sp1: ∼2-fold; survivin: ∼5-fold) and Western blot (Sp1: >2.6-fold; survivin: >100-fold). The Sp1 inhibitor, and anti-cancer small molecule, tolfenamic acid (TA), was tested to enhance the response of Cisplatin (Cis) in EOC cell lines. Cell viability (CellTiter-Glo), combination index (CalcuSyn software), apoptosis (Annexin-V staining), cell cycle analyses (flow cytometry), and reactive oxygen species (flow cytometry) were determined. Cell migration and invasion was assessed using matrigel coated transwell chambers. Agilent Technologies proteomics analysis identified potential signaling pathways involved. The combination of TA (50 µM) and Cis (5 µM) synergistically increased the growth inhibition in ES2 (∼80 %, p < 0.001) and OVCAR-3 (60 %, p < 0.001) cells. TA or TA + Cis treatment in ES2 cells caused cell cycle arrest in G1 Phase (TA) or S-Phase (TA + Cis) and unregulated reactive oxygen species. Invasion and migration was decreased in ES2 cells. Global proteomic profiling showed modulation of proteins associated with oxidative phosphorylation, apoptosis, electron transport chain, DNA damage, and cell cycle proteins. These results demonstrate an association of Sp1 and survivin in EOC and confirm targeting these candidates with TA potentially sensitizes EOC cells to cisplatin.

Comparative proteomics of the superior and inferior spikelets at the early grain filling stage in rice cultivars contrast for panicle compactness and ethylene evolution.

The breeding programmes in rice aimed at increasing the number of spikelets per panicle have been accompanied by poor grain filling in the inferior spikelets of large panicle rice, leading to yield disadvantage. The present study attempted to understand the reason for differential grain filling in the inferior and superior spikelets by comparative proteomics considering a compact-panicle rice cultivar Mahalaxmi and a lax-panicle rice cultivar Upahar, which show poor and good grain filling, respectively. An initial study of two rice cultivars for panicle compactness and grain filling revealed an inverse correlation between the two parameters. It was further observed that the panicle compactness in Mahalaxmi was associated with a higher evolution of ethylene by the spikelets, both superior and inferior, compared with the lax-panicle Upahar. The proteomic studies revealed that the superior and inferior spikelets of Mahalaxmi differentially expressed 21 proteins that were also expressed in Upahar. However, in Upahar, only two of these proteins were differentially expressed between the superior and inferior spikelets, indicating that the metabolic activities of the spikelets occupying the superior and inferior positions on the panicle were very different in Mahalaxmi compared with those in Upahar. Among the proteins that were downregulated in the inferior spikelets compared with the superior ones in Mahalaxmi were importin-α, elongation factor 1-ß and cell division control protein 48, which are essential for cell cycle progression and cell division. Low expression of these proteins might inhibit endosperm cell division in the inferior spikelets, limiting their sink capacity and leading to poor grain filling compared to that in the superior spikelets. The poor grain filling in Mahalaxmi may also be a result of the high evolution of ethylene in the inferior spikelets, which is reflected from the observation that these spikelets showed significantly higher expression of S-adenosylmethionine synthase and the gene encoding the enzyme than the superior spikelets in this cultivar, but not in Upahar; S-adenosynlmethionine synthase catalyses the synthesis of S-adenosylmethionine, the precursor of ethylene biosynthesis.

MicroRNAs as biomarkers and prospective therapeutic targets in colon and pancreatic cancers.

Colon and pancreatic cancers have high mortality rates due to early metastasis prior to the onset of symptoms. Screening tests for colorectal cancer are invasive and expensive. No effective screening is available for pancreatic cancer. Identification of biomarkers for early detection in both of these cancers is being extensively researched. MicroRNAs (miRNA) are small non-coding molecule biomarkers that regulate cancers. Measurement of miRNAs in pancreatic fluid or blood could be a preferred non-invasive screening method. The regulation of colon and pancreatic cancers by miRNA is complex. miRNA play a central role in inflammation, invasiveness, and tumor progression in these two cancers, as well as regulation of the NF-κB pathway. miRNA's evolving role in screening is also reviewed.

Biochemical and molecular characterisation of salt-induced poor grain filling in a rice cultivar.

Despite the prevalence of poor grain filling in rice (Oryza sativa L.) under abiotic stress, the reason for this is largely unexplored. Application of 0.75% NaCl to a salt-sensitive rice cultivar at late booting resulted in a >20% yield loss. Spikelets per panicle and the percentage of filled grain decreased significantly in response to NaCl application. The inhibitory effect of NaCl on grain filling was greater in basal than in apical spikelets. Sucrose synthase (SUS) activity was positively correlated with grain weight. The transcript levels of the SUS isoforms differed greatly: the levels of SUS2 increased significantly in response to salt; those of SUS4 decreased drastically. Gene expression studies of starch synthase and ADP-glucose pyrophosphorylase showed that the decreased transcript levels of one isoform was compensated by an increase in those of the other. Salt application also significantly increased the gene expression of the ethylene receptors and the ethylene signalling proteins. The increase in their transcript levels was comparatively greater in basal than in apical spikelets. Significant enhancement in the transcript levels of the ethylene receptors and the increase in the production of ethylene indicated that the salt-induced inhibition of grain filling might be mediated by ethylene. Additionally, the inhibition of chromosomal endoreduplication mediated by decreased transcript levels of B-type cyclin could explain poor grain filling under salt stress. A significant increase in the transcript levels of the ethylene-responsive factors in the spikelets during grain filling in response to salt indicated their possible protective role in grain filling under stress.

Identification and Characterization of Differentially Expressed Genes in Inferior and Superior Spikelets of Rice Cultivars with Contrasting Panicle-Compactness and Grain-Filling Properties.

Breeding programs for increasing spikelet number in rice have resulted in compactness of the panicle, accompanied by poor grain filling in inferior spikelets. Although the inefficient utilization of assimilate has been indicated as responsible for this poor grain filling, the underlying cause remains elusive. The current study utilized the suppression subtractive hybridization technique to identify 57 and 79 genes that overexpressed in the superior and inferior spikelets (with respect to each other), respectively, of the compact-panicle rice cultivar Mahalaxmi. Functional categorization of these differentially expressed genes revealed a marked metabolic difference between the spikelets according to their spatial location on the panicle. The expression of genes encoding seed storage proteins was dominant in inferior spikelets, whereas genes encoding regulatory proteins, such as serine-threonine kinase, zinc finger protein and E3 ligase, were highly expressed in superior spikelets. The expression patterns of these genes in the inferior and superior spikelets of Mahalaxmi were similar to those observed in another compact-panicle cultivar, OR-1918, but differed from those obtained in two lax-panicle cultivars, Upahar and Lalat. The results first suggest that the regulatory proteins abundantly expressed in the superior spikelets of compact-panicle cultivars and in both the superior and inferior spikelets of lax-panicle cultivars but poorly expressed in the inferior spikelets of compact-panicle cultivars promote grain filling. Second, the high expression of seed-storage proteins observed in the inferior spikelets of compact-panicle cultivars appears to inhibit the grain filling process. Third, the low expression of enzymes of the Krebs cycle in inferior spikelets compared with superior spikelets of compact-panicle cultivars is bound to lead to poor ATP generation in the former and consequently limit starch biosynthesis, an ATP-consuming process, resulting in poor grain filling.

Spikelet-specific variation in ethylene production and constitutive expression of ethylene receptors and signal transducers during grain filling of compact- and lax-panicle rice (Oryza sativa) cultivars.

Grain yields in modern super rice cultivars do not always meet the expectations because many spikelets are located on secondary branches in closely packed homogeneous distribution in these plants, and they do not fill properly. The factors limiting grain filling of such spikelets, especially in the lower panicle branches, are elusive. Two long-duration rice cultivars differing in panicle density, Mahalaxmi (compact) and Upahar (lax), were cultivated in an open field plot. Grain filling, ethylene production and constitutive expression of ethylene receptors and ethylene signal transducers in apical and basal spikelets of the panicle were compared during the early post-anthesis stage, which is the most critical period for grain development. In another experiment, a similar assessment was made for the medium-duration cultivars compact-panicle OR-1918 and lax-panicle Lalat. Grain weight of the apical spikelets was always higher than that of the basal spikelets. This gradient of grain weight was wide in the compact-panicle cultivars and narrow in the lax-panicle cultivars. Compared to apical spikelets, the basal spikelets produced more ethylene at anthesis and retained the capacity for post-anthesis expression of ethylene receptors and ethylene signal transducers longer. High ethylene production enhanced the expression of the RSR1 gene, but reduced expression of the GBSS1 gene. Ethylene inhibited the partitioning of assimilates of developing grains resulting in low starch biosynthesis and high accumulation of soluble carbohydrates. It is concluded that an increase in grain/spikelet density in rice panicles reduces apical dominance to the detriment of grain filling by production of ethylene and/or enhanced perception of the ethylene signal. Ethylene could be a second messenger for apical dominance in grain filling. The manipulation of the ethylene signal would possibly improve rice grain yield.