Abstract
Hymenoglossum cruentum (Hymenophyllaceae) is a poikilohydric, homoiochlorophyllous desiccation-tolerant (DT) epiphyte fern. It can undergo fast and frequent dehydration-rehydration cycles. This fern is highly abundant at high-humidity/low-light microenvironments within the canopy, although rapid changes in humidity and light intensity are frequent. The objective of this research is to identify genes associated to desiccation-rehydration cycle in the transcriptome of H. cruentum to better understand the genetic dynamics behind its desiccation tolerance mechanism. H. cruentum plants were subjected to a 7 days long desiccation-rehydration process and then used to identify key expressed genes associated to its capacity to dehydrate and rehydrate. The relative water content (RWC) and maximum quantum efficiency (Fv/Fm) of H. cruentum fronds decayed to 6% and 0.04, respectively, at the end of the desiccation stage. After re-watering, the fern showed a rapid recovery of RWC and Fv/Fm (ca. 73% and 0.8, respectively). Based on clustering and network analysis, our results reveal key genes, such as UBA/TS-N, DYNLL, and LHC, orchestrating intracellular motility and photosynthetic metabolism; strong balance between avoiding cell death and defense (CAT3, AP2/ERF) when dehydrated, and detoxifying pathways and stabilization of photosystems (GST, CAB2, and ELIP9) during rehydration. Here we provide novel insights into the genetic dynamics behind the desiccation tolerance mechanism of H. cruentum.
Highlights
A major problem that plants have faced since they colonized earth’s surface is the exposure to a high atmospheric demand of water
From the accumulation patterns of transcripts observed in the Self-Organizing Maps (SOM) analysis, we identify and quantify the expression of 26 candidates differentially expressed genes (DEGs) potentially key for the desiccation tolerance response of H. cruentum (Supplementary Dataset S5)
Most of the studies describing the desiccation tolerance response have focused on plants that dehydrate and rehydrate slowly (Giarola and Bartels, 2015; Giarola et al, 2016; Liu et al, 2018)
Summary
A major problem that plants have faced since they colonized earth’s surface is the exposure to a high atmospheric demand of water. Among the different degrees of water deficit, desiccation is the most extreme form of dehydration. It occurs when most of the protoplasmic water is lost and only a very small amount of tightly bound water remains in the cell matrix (Djilianov et al, 2013). An exceptional and small group of plants, called “resurrection plants,” can tolerate extreme desiccation (less than ∼5% of water content), and restore their metabolism completely when rehydrated (Ingram and Bartels, 1996; Alpert, 2000). Desiccation tolerant plants occur in phylogenetic distinct clades, along a wide range of environments. Must integrate the perception and signaling of water loss, the protection of cellular components, and an efficient cellular repair activity (Alpert, 2000; Oliver et al, 2000)
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