Noreen Bibi

A novel NAP member GhNAP is involved in leaf senescence in Gossypium hirsutum

Highlight GhNAP could regulate leaf senescence via the ABA-mediated pathways and is related to the yield and quality of cotton.

Molecular Evolution and Expansion Analysis of the NAC Transcription Factor in Zea mays

NAC (NAM, ATAF1, 2 and CUC2) family is a plant-specific transcription factor and it controls various plant developmental processes. In the current study, 124 NAC members were identified in Zea mays and were phylogenetically clustered into 13 distinct subfamilies. The whole genome duplication (WGD), especially an additional WGD event, may lead to expanding ZmNAC members. Different subfamily has different expansion rate, and NAC subfamily preference was found during the expansion in maize. Moreover, the duplication events might occur after the divergence of the lineages of Z. mays and S. italica, and segmental duplication seemed to be the dominant pattern for the gene duplication in maize. Furthermore, the expansion of ZmNAC members may be also related to gain and loss of introns. Besides, the restriction of functional divergence was discovered after most of the gene duplication events. These results could provide novel insights into molecular evolution and expansion analysis of NAC family in maize, and advance the NAC researches in other plants, especially polyploid plants.

The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

Abstract Low phosphorus (LP) limits crop growth and productivity in the majority of arable lands worldwide. Here, we investigated the changes in physiological and biochemical traits of Tibetan wild barleys (Hordeum vulgare L. ssp. spontaneum) XZ99 (LP tolerant), XZ100 (LP sensitive), and cultivated barley ZD9 (moderately LP tolerant) under two phosphorus (P) levels during vegetative stage. These genotypes showed considerable differences in the change of biomass accumulation, root/shoot dry weight ratio, root morphology, organic acid secretion, carbohydrate metabolism, ATPase (Adenosine triphosphatase) activity, P concentration and accumulation under LP in comparison with CK (control) condition. The higher LP tolerance of XZ99 is associated with more developed roots, enhanced sucrose biosynthesis and hydrolysis of carbohydrate metabolism pathway, higher APase (Acid phosphatase) and ATPase activity, and more secretion of citrate and succinate in roots when plants are exposed to LP stress. The results prove the potential of Tibetan wild barley in developing barley cultivars with high tolerance to LP stress and understanding the mechanisms of LP tolerance in plants.

Improvements of Fertility Restoration in Cytoplasmic Male Sterile Cotton by Enhanced Expression of Glutathione S-Transferase (GST) Gene

The molecular and biochemical bases of fertility restoration were explored using cytoplasmic male sterile (CMS) Ji A, maintainer Ji B, and two cotton hybrids RF1 and QF1, developed by crossing CMS with DES-HAF277 (normal restorer) and Zheda strong restorer (transgenic restorer with GST gene), respectively. Transcript levels of both exogenous and endogenous GST genes were high in anther as compared to other plant tissues of the QF1 hybrid. Moreover, the expression of the GST gene during meiosis (stage 2) and microspore development (stage 3) was highest in the QF1 hybrid. The ratio of cyanide-resistant respiration to total respiration was also high in the QF1 hybrid during stage 2 and stage 3 as compared to the RF1 hybrid. O2− and H2O2 contents increased more during stage 2 in the CMS line and stage 3 in the RF1 hybrid compared to the maintainer and QF1 hybrid. Similarly, MDA contents were at a maximum in CMS followed by the RF1, QF1, and the maintainer line during the whole course of anther development. In addition, the activities of antioxidant enzymes (SOD, POD, CAT, APX, GST, GR, and DHAR) and contents of non-enzymatic antioxidants (GSH and ASA) were elevated in the QF1 hybrid as compared to the RF1 hybrid, during the whole course of anther development. The present study suggests that the introgression of the GST gene into restorer lines could be a potential way to enhance restoration capability by maintaining the equilibrium between oxidative stress and scavenging enzymes, and might favor healthier development of microspores.

Molecular evolution and species-specific expansion of the NAP members in plants

The NAP (NAC-Like, Activated by AP3 /PI) subfamily is one of the important plant-specific transcription factors, and controls many vital biological processes in plants. In the current study, 197 NAP proteins were identified from 31 vascular plants, but no NAP members were found in eight non-vascular plants. All NAP proteins were phylogenetically classified into two groups (NAP I and NAP II), and the origin time of the NAP I group might be relatively later than that of the NAP II group. Furthermore, species-specific gene duplications, caused by segmental duplication events, resulted in the expansion of the NAP subfamily after species-divergence. Different groups have different expansion rates, and the NAP group preference was found during the expansion in plants. Moreover, the expansion of NAP proteins may be related to the gain and loss of introns. Besides, functional divergence was limited after the gene duplication. Abscisic acid (ABA) might play an important role in leaf senescence, which is regulated by NAP subfamily. These results could lay an important foundation for expansion and evolutionary analysis of NAP subfamily in plants.

Genomic Identification and Comparative Expansion Analysis of the Non-Specific Lipid Transfer Protein Gene Family in Gossypium

Plant non-specific lipid transfer proteins (nsLTPs) are involved in many biological processes. In this study, 51, 47 and 91 nsLTPs were identified in Gossypium arboreum, G. raimondii and their descendant allotetraploid G. hirsutum, respectively. All the nsLTPs were phylogenetically divided into 8 distinct subfamilies. Besides, the recent duplication, which is considered cotton-specific whole genome duplication, may have led to nsLTP expansion in Gossypium. Both tandem and segmental duplication contributed to nsLTP expansion in G. arboreum and G. hirsutum, while tandem duplication was the dominant pattern in G. raimondii. Additionally, the interspecific orthologous gene pairs in Gossypium were identified. Some GaLTPs and GrLTPs lost their orthologs in the At and Dt subgenomes, respectively, of G. hirsutum. The distribution of these GrLTPs and GaLTPs within each subfamily was complementary, suggesting that the loss and retention of nsLTPs in G. hirsutum might not be random. Moreover, the nsLTPs in the At and Dt subgenomes might have evolved symmetrically. Furthermore, both intraspecific and interspecific orthologous genes showed considerable expression variation, suggesting that their functions were strongly differentiated. Our results lay an important foundation for expansion and evolutionary analysis of the nsLTP family in Gossypium, and advance nsLTP studies in other plants, especially polyploid plants.

In vitro inhibition of pigmentation and fiber development in colored cotton

Colored cotton has naturally pigmented fibers. The mechanism of pigmentation in cotton fiber is not well documented. This experiment was conducted to study the effects of respiratory chain inhibitors, i.e., rotenone and thiourea, on pigmentation and fiber development in colored cotton. After 1 d post-anthesis, ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d. The results demonstrate that both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions, and the inhibition efficiency of rotenone was much higher than that of thiourea. Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton. In green cotton fiber, rotenone advanced fiber pigment development by 7 d at 200 μmol/L, while thiourea inhibited fiber pigmentation at all treatment levels (400, 600, 800, 1 000, and 2 000 μmol/L). Both respiratory inhibitors, however, had no significant effects on pigmentation of brown cotton fibers. The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors. It is suggested that both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton.

FROM Qutn TO Bt COTTON: DEVELOPMENT, ADOPTION AND PROSPECTS. A REVIEW.

Cotton has unique history of domestication, diversification, and utilization. Globally it is an important cash crop that provides raw material for textile industry. The story of cotton started from human civilization and the climax arrived with the efforts of developing transgenic cotton for various traits. Though conventional breeding brought steady improvement in developing resistance against biotic stresses but recent success story of gene transfer from Bacillus thuringiensis into cotton showed game changing effects on cotton cultivation. Amongst various families of insecticidal proteins Bt Cry-toxins received more attention because of specificity against receptors on the cell membranes of insect midgut epithelial cells. Rapid Bt cotton adoption by farmers due to its economic and environmental benefits has changed the landscape of cotton cultivation in many countries. But the variable expression of Bt transgene in the newly developed Bt cotton genotypes in tropical environment is questionable. Variability of toxin level in different plant parts at various life stage of plant is an outcome of genotypic interaction with environmental factors. Temporal gene expression of Cry1Ac is also blamed for the epigenetic background in which transgene has been inserted. The presence of genotypes with sub-lethal level of Bt toxin might create resistance in Lepidopteron insects, limiting the use of Bt cotton in future, with the opportunity for other resistance development strategies to get more attention like gene stacking. Until the farmers get access to more recent technology, best option is to delay the development of resistance by applying Insect Resistance Management (IRM) strategies.

Tolerance to Combined Stress of Drought and Salinity in Barley

Drought and salinity, frequently co-occurring in both natural and agricultural ecosystems, are the most important abiotic stresses limiting agricultural production worldwide. Therefore, an improvement in drought and salinity tolerance in crops is a prerequisite for achieving economic gains. Barley, being one of the most tolerant cereal crops for drought and salinity, possesses tremendous potential as an ideal model crop for drought and salinity tolerance. Wild barley (Hordeum vulgare ssp. spontaneum or ssp. agriocrithum) was demonstrated as a key genetic resource for the tolerance to both stresses. Currently, plant morphology, physiology, and biochemistry have provided new insights to understand drought-tolerant traits. Improvement for drought and salinity tolerance can be achieved by the introduction of drought- and salt-tolerance-related genes and quantitative trait loci (QTLs) to modern barley cultivars. Therefore, the identification of candidate loci involved in drought and salinity tolerance using omics and QTL mapping is necessary. Drought/salinity-responsive genes and QTLs have been identified in both cultivated and wild barleys and have great potential for genetic improvement of barley. Combining tolerant genes and QTLs in crop-breeding programs aimed at improving tolerance to drought and salinity will be achieved within a multidisciplinary context. This strategy will lead to new cultivars highly tolerant to drought and salinity with high yield potential and stability in dry environments.