Abstract
Research Highlights: Phenotypic changes and expression profiles, phylogeny, conserved motifs, and expression correlations of NAC (NAM, ATAF1, ATAF2 and CUC2) transcription factors (TFs) in blueberry genome were detected under drought stress, and the expression patterns and functions of 12 NACs were analyzed. Background and Objectives: Blueberry is an important shrub species with a high level of flavonoids in fruit, which are implicated in a broad range of health benefits. However, the molecular mechanism of this shrub species in response to drought stress still remains elusive. NAC TFs widely participate in stress tolerance in many plant species. The characterization and expression profiles of NAC TFs were analyzed on the basis of genome data in blueberry when subjected to drought stress. Materials and Methods: Combined with the analysis of chlorophyll a fluorescence and endogenous phytohormones, the phenotypic changes of blueberry under drought stress were observed. The phylogenetic tree, conserved motifs, differently expressed genes, and expression correlation were determined by means of multiple bioinformatics analysis. The expression profiles of NACs in different organs were examined and compared through RNA-seq and qRT-PCR assay. Results: The chlorophyll a fluorescence parameters φPo, φEo, φRo, and PIabs of leaves were significantly inhibited under drought stress. ABA (abscisic acid) content noticeably increased over the duration of drought, whereas GA3 (gibberellic acid) and IAA (indole acetic acid) content decreased continuously. A total of 158 NACs were identified in blueberry genome and 62 NACs were differently expressed in leaf and root of blueberry under drought stress. Among them, 14 NACs were significantly correlated with the expression of other NAC genes. Conclusions: Our results revealed the phenotypic changes of this shrub under drought stress and linked them with NAC TFs, which are potentially involved in the process of response to drought stress.
Highlights
Blueberry (Vaccinium corymbosum L.) is a perennial shrub within the genus Vaccinium of the familyEricaceae that has attracted a lot of attention due to its rich nutrients, especially anthocyanins [1].Anthocyanins have been demonstrated to affect the color formation of fruit, and can improve the antioxidant capacity and prevent a variety of diseases such as cancer [2]
Changes in morphology of leaves usually tend to indicate the leaves of blueberry turned slightly yellow and wilted, began to dry and completely withered changes in chlorophyll a fluorescence, we further examined the changes of φPo, φtoEo, φRo, after severe drought stress treatment (Figure 1a)
We found that the efficiency of light energy conversion through chlorophyll a fluorescence parameters such as φPo, φEo, φRo, and PIabs in blueberry seedling leaves constantly decreased with the drought degree aggravated, suggesting that drought stress decreased the capacity of photosynthetic energy utilization in blueberry seedling leaves, which led to an imbalance between photosynthetic light absorption and energy utilization
Summary
Blueberry (Vaccinium corymbosum L.) is a perennial shrub within the genus Vaccinium of the family. Anthocyanins have been demonstrated to affect the color formation of fruit, and can improve the antioxidant capacity and prevent a variety of diseases such as cancer [2]. To date, most studies on blueberries have focused on the research of anthocyanin formation and regulation mechanism [3,4]. In recent years, with global warming and frequency of adversity [5], the survival of blueberry tree is often threatened by drought stress, and the output is further affected. It is necessary to reveal the drought tolerance mechanism of blueberry, as this would contribute to the selective breeding of resistant variety in the shrub species.
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