Transcriptome analysis of drought-tolerant sorghum genotype SC56 in response to water stress reveals an oxidative stress defense strategy.

Drought tolerance is a crucial trait for crops to curtail the yield loss inflicted by water stress, yet genetic improvement efforts are challenged by the complexity of this character. The adaptation of sorghum to abiotic stress, its genotypic variability, and relatively small genome make this species well-suited to dissect the molecular basis of drought tolerance. The use of differential transcriptome analysis provides a snapshot of the bioprocesses underlying drought response as well as genes that might be determinants of the drought tolerance trait. RNA sequencing data were analyzed via gene ontology enrichment to compare the transcriptome profiles of two sorghum lines, the drought-tolerant SC56 and the drought-sensitive Tx7000. SC56 outperformed Tx7000 in wet conditions by upregulating processes driving growth and guaranteeing homeostasis. The drought tolerance of SC56 seems to be an intrinsic trait occurring through overexpressing stress tolerance genes in wet conditions, notably genes acting in defense against oxidative stress (SOD1, SOD2, VTC1, MDAR1, MSRB2, and ABC1K1). Similarly to wet conditions, under drought, SC56 enhanced its transmembrane transport and maintained growth-promoting mechanisms. Under drought, SC56 also upregulated stress tolerance genes that heighten the antioxidant capacity (SOD1, RCI3, VTE1, UCP1, FD1, and FD2), regulatory factors (CIPK1 and CRK7), and repressors of premature senescence (SAUL1). The differential expression analysis uncovered biological processes which upregulation enables SC56 to be a better accumulator of biomass and connects the drought tolerance trait to key stress tolerance genes, making this genotype a judicious choice for isolation of tolerance genes.

Transcriptional response of honey bee (Apis mellifera) to differential nutritional status and Nosema infection.

BACKGROUND: Bees are confronting several environmental challenges, including the intermingled effects of malnutrition and disease. Intuitively, pollen is the healthiest nutritional choice, however, commercial substitutes, such as Bee-Pro and MegaBee, are widely used. Herein we examined how feeding natural and artificial diets shapes transcription in the abdomen of the honey bee, and how transcription shifts in combination with Nosema parasitism. RESULTS: Gene ontology enrichment revealed that, compared with poor diet (carbohydrates [C]), bees fed pollen (P > C), Bee-Pro (B > C), and MegaBee (M > C) showed a broad upregulation of metabolic processes, especially lipids; however, pollen feeding promoted more functions, and superior proteolysis. The superiority of the pollen diet was also evident through the remarkable overexpression of vitellogenin in bees fed pollen instead of MegaBee or Bee-Pro. Upregulation of bioprocesses under carbohydrates feeding compared to pollen (C > P) provided a clear poor nutritional status, uncovering stark expression changes that were slight or absent relatively to Bee-Pro (C > B) or MegaBee (C > M). Poor diet feeding (C > P) induced starvation response genes and hippo signaling pathway, while it repressed growth through different mechanisms. Carbohydrate feeding (C > P) also elicited 'adult behavior', and developmental processes suggesting transition to foraging. Finally, it altered the 'circadian rhythm', reflecting the role of this mechanism in the adaptation to nutritional stress in mammals. Nosema-infected bees fed pollen compared to carbohydrates (PN > CN) upheld certain bioprocesses of uninfected bees (P > C). Poor nutritional status was more apparent against pollen (CN > PN) than Bee-Pro (CN > BN) or MegaBee (CN > MN). Nosema accentuated the effects of malnutrition since more starvation-response genes and stress response mechanisms were upregulated in CN > PN compared to C > P. The bioprocess 'Macromolecular complex assembly' was also enriched in CN > PN, and involved genes associated with human HIV and/or influenza, thus providing potential candidates for bee-Nosema interactions. Finally, the enzyme Duox emerged as essential for guts defense in bees, similarly to Drosophila. CONCLUSIONS: These results provide evidence of the superior nutritional status of bees fed pollen instead of artificial substitutes in terms of overall health, even in the presence of a pathogen.

Connecting the nutrient composition of seasonal pollens with changing nutritional needs of honey bee (Apis mellifera L.) colonies.

Free-ranging herbivores have yearly life cycles that generate dynamic resource needs. Honey bee colonies also have a yearly life cycle that might generate nutritional requirements that differ between times of brood rearing and colony expansion in the spring and population contraction and preparation for overwintering in the fall. To test this, we analyzed polyfloral mixes of spring and fall pollens to determine if the nutrient composition differed with season. Next, we fed both types of seasonal pollens to bees reared in spring and fall. We compared the development of brood food glands (i.e., hypopharyngeal glands - HPG), and the expression of genes in the fat body between bees fed pollen from the same (in-season) or different season (out-of-season) when they were reared. Because pathogen challenges often heighten the effects of nutritional stress, we infected a subset of bees with Nosema to determine if bees responded differently to the infection depending on the seasonal pollen they consumed. We found that spring and fall pollens were similar in total protein and lipid concentrations, but spring pollens had higher concentrations of amino and fatty acids that support HPG growth and brood production. Bees responded differently when fed in vs. out of season pollen. The HPG of both uninfected and Nosema-infected spring bees were larger when they were fed spring (in-season) compared to fall pollen. Spring bees differentially regulated more than 200 genes when fed in- vs. out-of-season pollen. When infected with Nosema, approximately 400 genes showed different infection-induced expression patterns in spring bees depending on pollen type. In contrast, HPG size in fall bees was not affected by pollen type, though HPG were smaller in those infected with Nosema. Very few genes were differentially expressed with pollen type in uninfected (4 genes) and infected fall bees (5 genes). Pollen type did not affect patterns of infection-induced expression in fall bees. Our data suggest that physiological responses to seasonal pollens differ between bees reared in the spring and fall with spring bees being significantly more sensitive to pollen type especially when infected with Nosema. This study provides evidence that seasonal pollens may provide levels of nutrients that align with the activities of honey bees during their yearly colony cycle. The findings are important for the planning and establishment of forage plantings to sustain honey bees, and in the development of seasonal nutritional supplements fed to colonies when pollen is unavailable.