Abstract
Agave, monocotyledonous succulent plants, is endemic to arid regions of North America, exhibiting exceptional tolerance to their xeric environments. They employ various strategies to overcome environmental constraints, such as crassulacean acid metabolism, wax depositions, and protective leaf morphology. Genomic resources of Agave species have received little attention irrespective of their cultural, economic and ecological importance, which so far prevented the understanding of the molecular bases underlying their adaptations to the arid environment. In this study, we aimed to elucidate molecular mechanism(s) using transcriptome sequencing of A. sisalana. A de novo approach was applied to assemble paired-end reads. The expression study unveiled 3,095 differentially expressed unigenes between well-irrigated and drought-stressed leaf samples. Gene ontology and KEGG analysis specified a significant number of abiotic stress responsive genes and pathways involved in processes like hormonal responses, antioxidant activity, response to stress stimuli, wax biosynthesis, and ROS metabolism. We also identified transcripts belonging to several families harboring important drought-responsive genes. Our study provides the first insight into the genomic structure of A. sisalana underlying adaptations to drought stress, thus providing diverse genetic resources for drought tolerance breeding research.
Highlights
Drought is one of the major abiotic stresses, which significantly diminishes the agricultural production and threatens food security worldwide[1]
As per GOSlim distribution, most transcripts were related to the biological process (BP) 58.2%, molecular functions (MF) 43.2% and cellular components (CC) 35.7%. (Supplementary Dataset 2 S1)
Total 1178 differentially expressed unigenes (DEG) were predicted as the potential transcription factors (TFs) under drought stress in A. sisalana transcriptome, and were further classified into 52 subfamilies (Supplementary Dataset 4-S1)
Summary
Drought is one of the major abiotic stresses, which significantly diminishes the agricultural production and threatens food security worldwide[1]. We obtained 129 biochemical pathways with the involvement of 6338 unigenes based on KEGG database prediction (http://genome.jp/kegg/) under drought stress (Supplementary Dataset 2 S2, S3). These unigenes were further categorized into five diverse functional groups, namely metabolism (93.4%), the organismal system (4.5%), environmental information processing (0.72%), genetic information processing and cellular processes (0.78%) (Fig. 3). Total 1178 DEGs were predicted as the potential TFs under drought stress in A. sisalana transcriptome, and were further classified into 52 subfamilies (Supplementary Dataset 4-S1) Majority of these genes belonged to ERF family (102), bHLH (100), NAC group (86), MYB_ releated (84), C2H2 group (58), WRKY family (46), HSFs (33) and others (Fig. 6A). All of them were down-regulated under drought stress including CAB1 (chlorophyll A/B binding protein 1 and 6), LHB1B1 light-harvesting chlorophyll-protein complex II subunit B1, PSAD -2, PSAF, PSAG, PSAH2, PSAK, PSAL, PSAN (involved in photosystem I), PSB group with subunits (components of photosystem II) and others related to ATPase synthesis (Supplementary Dataset 4-S2)
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