Major intrinsic proteins repertoire of Morus notabilis and their expression profiles in different species

Comparative transcriptomics of leaves of five mulberry accessions and cataloguing structural and expression variants for future prospects

Bombyx mori, a monophagous insect, prefers leaves of the certain species of Morus more than others. The preference has been attributed to morphological and anatomical features and biochemical compounds. In the present manuscript a comparison has been made among the transcriptome of leaves of the two preferred cultivated varieties and three wild types species. While assembling, high quality transcriptomes of five genotypes were constructed with a total of 100930, 151245, 89724, 181761 and 102908 transcripts from ML, MN, MS, K2 and V1 samples respectively. Further, to compare them, orthologs were identified from these assembled transcriptome. A total of 22462, 23413, 23685, 24371, 18362, 22326, 20058, 18049, 17567 and 20518 clusters of orthologs were found in one to one comparison in KvsN, KvsL, KvsS, KvsV, LvsN, LvsS, LvsV, NvsS, NvsV, and SvsV respectively. 4236 orthologs with algebraic connectivity of 1.0 were then used to compare and to find out differentially expressed transcripts from all the genotypes. A total of 1037 transcripts expressed that include some of the important morphology, anatomy and biochemical pathways regulating transcription factors (AP2/ERFs and C2H2 Zinc fingers) and signalling components were identified to express differentially. Further, these transcriptomes were used find out markers (SSR) and variants and a total of 1101013, 537245, 970877, 310437, 675772, 338400, 581189, 751477, 514999 and 257107 variants including SNP, MNP, Insertions and deletions were found in one to one comparisons. Taken together, our data could be highly useful for mulberry community worldwide as it could be utilized in mulberry breeding programs.

Physiological and PIP Transcriptional Responses to Progressive Soil Water Deficit in Three Mulberry Cultivars

Although mulberry cultivars Wubu, Yu711, and 7307 display distinct anatomical, morphological, and agronomic characteristics under natural conditions, it remains unclear if they differ in drought tolerance. To address this question and elucidate the underlying regulatory mechanisms at the whole-plant level, 2-month old saplings of the three mulberry cultivars were exposed to progressive soil water deficit for 5 days. The physiological responses and transcriptional changes of PIPs in different plant tissues were analyzed. Drought stress led to reduced leaf relative water content (RWC) and tissue water contents, differentially expressed PIPs, decreased chlorophyll and starch, increased soluble sugars and free proline, and enhanced activities of antioxidant enzymes in all plant parts of the three cultivars. Concentrations of hydrogen peroxide (H2O2), superoxide anion (O2 •-), and malonaldehyde (MDA) were significantly declined in roots, stimulated in leaves but unaltered in wood and bark. In contrast, except the roots of 7307, soluble proteins were repressed in roots and leaves but induced in wood and bark of the three cultivars in response to progressive water deficit. These results revealed tissue-specific drought stress responses in mulberry. Comparing to cultivar Yu711 and 7307, Wubu showed generally slighter changes in leaf RWC and tissue water contents at day 2, corresponding well to the steady PIP transcript levels, foliar concentrations of chlorophyll, O2 •-, MDA, and free proline. At day 5, Wubu sustained higher tissue water contents in green tissues, displayed stronger responsiveness of PIP transcription, lower concentrations of soluble sugars and starch, lower foliar MDA, higher proline and soluble proteins, higher ROS accumulation and enhanced activities of several antioxidant enzymes. Our results indicate that whole-plant level responses of PIP transcription, osmoregulation through proline and soluble proteins and antioxidative protection are important mechanisms for mulberry to cope with drought stress. These traits play significant roles in conferring the relatively higher drought tolerance of cultivar Wubu and could be potentially useful for future mulberry improvement programmes.

Identification of Triticum aestivum nsLTPs and functional validation of two members in development and stress mitigation roles

Role of plant nsLTP in biotic stress is well reported; however, their role during abiotic stress is far from clear. This study comprises genome-wide identification of LTPs and characterizes the regulation and function of two Triticum aestivum lipid transfer proteins, TaLTP40 and TaLTP75, under stresses that influence membrane fluidity. A total of 105 LTP gene family members have been identified. The selected LTPs for functional validation were highly expressed during salt, cold and drought stress. Further, selected LTPs showed differential expression thermotolerant and thermosusceptible wheat cultivars. Higher expression of many TaLTPs was observed under different abiotic stresses in thermotolerant wheat cultivars as compared to thermosusceptible cultivars. TaLTPs regulation was correlated with light energy distribution studies under similar stress conditions. Cellular localization revealed localization of different TaLTPs to the tonoplast membrane along with the organelles involved in the secretory pathway. Induction of TaLTPs was observed upon treatment with dimethylsulphoxide. TaLTP40 and TaLTP75 overexpressing transgenic Arabidopsis showed a constitutively enhanced salt tolerance. Both the TaLTP40 and TaLTP75 overexpressing lines performed better in terms of chlorophyll a fluorescence, total chlorophyll content, membrane injury index, total biomass, percentage germination, percentage survival and relative growth rate. Hence, our analyses indicate that TaLTPs expression might be driven by change in membrane fluidity and could be involved in transferring membrane lipids to the biological membranes thus imparting tolerance to various abiotic stresses.

Auxin Response Factor Genes Repertoire in Mulberry: Identification, and Structural, Functional and Evolutionary Analyses

Auxin Response Factors (ARFs) are at the core of the regulation mechanism for auxin-mediated responses, along with AUX/IAA proteins.They are critical in the auxin-mediated control of various biological responses including development and stress. A wild mulberry species genome has been sequenced and offers an opportunity to investigate this important gene family. A total of 17 ARFs have been identified from mulberry (Morus notabilis) which show a wide range of expression patterns. Of these 17 ARFs, 15 have strong acidic isoelectric point (pI) values and a molecular mass ranging from 52 kDa to 101 kDa. The putative promoters of these ARFs harbour cis motifs related to light-dependent responses, various stress responses and hormone regulations suggestive of their multifactorial regulation. The gene ontology terms for ARFs indicate their role in flower development, stress, root morphology and other such development and stress mitigation related activities. Conserved motif analysis showed the presence of all typical domains in all but four members that lack the PB1 domain and thus represent truncated ARFs. Expression analysis of these ARFs suggests their preferential expression in tissues ranging from leaf, root, winter bud, bark and male flowers. These ARFs showed differential expression in the leaf tissue of M. notabilis, Morus laevigata and Morus serrata. Insights gained from this analysis have implications in mulberry improvement programs.