Abstract Hancornia speciosaGomes, a native fruit tree, plays an important socio-economic role in Brazil's traditional communities. The objective was to estimate the genetic structure of 176 individuals from eight locations in the Cerrado, Caatinga and Atlantic Forest biomes, based on six microsatellite markers. The analyzes revealed the formation of five population groups: A- Pernambuco, Paraíba and Sergipe (Atlantic Forest), B- Maranhão (Cerrado); both, var. speciosa, C- Bahia (Caatinga / Cerrado transition zone) and Ceará (Caatinga), D- Goiás (Cerrado) and E- Minas Gerais (Cerrado,) being groups C, D and E possibly var. pubescens. Most of the genetic variation is within the groups (65.61%, Fst = 0.34, p <0.001). Although group A had the highest Ho (0.66), it had a negative fixation index (f = -0.02), while the other had positive values. Our results revealed high levels of genetic diversity and provide support the development of more efficient conservation strategies for H. speciosa.

RESUMO: O objetivo do estudo foi analisar a expressão de genes de referência em cana-de-açúcar sob estresse hídrico. As cultivares RB72454 e RB72910 foram cultivadas em campo e os tratamentos controle e estresse foram aplicados após 135 dias. O estresse das plantas foi mensurado utilizando as variáveis fisiológicas: taxa fotossintética, transpiração e condutância estomática. Para cada repetição biológica, a expressão gênica foi conduzida usando PCR tempo real para os genes α-tubulina, β-tubulina, β-actina, ciclofilina, fator 1 de alongamento eucariótico, gliceraldeído 3-fosfato desidrogenase (GAPDH), histona H3 e ubiquitina. A estabilidade dos genes foi avaliada usando os softwares geNorm,NormFinder e BestKeeper. Entre os genes candidatos, GAPDH foi identificado como o mais estável nos três métodos de análises, indicando ser estável para estudos de expressão gênica em cana-de-açúcar sob estresse hídrico; seguindo o gene β-actina como o segundo mais estável. Os resultados concluem que os genes GAPDH e β-actina são indicados para normalização em expressão gênica relativa, associada com estresse hídrico em cana-de-açúcar.

ABSTRACT: The aim of this study was to analyze the expression of putative reference genes in sugarcane under drought stress. The varieties RB72454 and RB72910 were cultivated and the treatments control and drought stress applied to 135-day-old plants grown under field conditions. The stress level of the plants was measured by rate of photosynthesis, transpiration, and stomatal conductance. For each biological replicate, expression analyses were conducted using quantitative polymerase chain reaction for the genes α-tubulin, β-tubulin, β-actin, cyclophilin, eukaryotic elongation factor 1, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), histone H3 and ubiquitin. Stability was evaluated using the geNorm, NormFinder, and BestKeeper software packages. Among the candidate genes, GAPDH was identified as the most stable in all software, indicating its suitability for gene expression studies in sugarcane undergoing drought stress; the gene β-actin was the second most stable. These findings suggest using GAPDH and β-actin for normalization in relative gene expression in sugarcane.

Abstract Drought is a major factor in decreased sugarcane productivity because of the resulting morphophysiological effects that it causes. Gene expression studies that have examined the influence of water stress in sugarcane have yielded divergent results, indicating the absence of a fixed pattern of changes in gene expression. In this work, we investigated the expression profiles of 12 genes in the leaves of a drought-tolerant genotype (RB72910) of sugarcane and compared the results with those of other studies. The genotype was subjected to 80–100% water availability (control condition) and 0–20% water availability (simulated drought). To analyze the physiological status, the SPAD index, Fv/Fm ratio, net photosynthesis (A), stomatal conductance (gs) and stomatal transpiration (E) were measured. Total RNA was extracted from leaves and the expression of SAMDC, ZmPIP2-1 protein, ZmTIP4-2 protein, WIP protein, LTP protein, histone H3, DNAj, ferredoxin I, β-tubulin, photosystem I, gene 1 and gene 2 was analyzed by quantitative real-time PCR (RT-PCR). Important differences in the expression profiles of these genes were observed when compared with other genotypes, suggesting that complex defense mechanisms are activated in response to water stress. However, there was no recognizable pattern for the changes in expression of the different proteins associated with tolerance to drought stress.