Abstract
A subset of genes in Arabidopsis thaliana is known to be up-regulated in response to a wide range of different environmental stress factors. However, not all of these genes are characterized as yet with respect to their functions. In this study, we used transgenic knockout, overexpression and reporter gene approaches to try to elucidate the biological roles of five unknown multiple-stress responsive genes in Arabidopsis. The selected genes have the following locus identifiers: At1g18740, At1g74450, At4g27652, At4g29780 and At5g12010. Firstly, T-DNA insertion knockout lines were identified for each locus and screened for altered phenotypes. None of the lines were found to be visually different from wildtype Col-0. Secondly, 35S-driven overexpression lines were generated for each open reading frame. Analysis of these transgenic lines showed altered phenotypes for lines overexpressing the At1g74450 ORF. Plants overexpressing the multiple-stress responsive gene At1g74450 are stunted in height and have reduced male fertility. Alexander staining of anthers from flowers at developmental stage 12–13 showed either an absence or a reduction in viable pollen compared to wildtype Col-0 and At1g74450 knockout lines. Interestingly, the effects of stress on crop productivity are most severe at developmental stages such as male gametophyte development. However, the molecular factors and regulatory networks underlying environmental stress-induced male gametophytic alterations are still largely unknown. Our results indicate that the At1g74450 gene provides a potential link between multiple environmental stresses, plant height and pollen development. In addition, ruthenium red staining analysis showed that At1g74450 may affect the composition of the inner seed coat mucilage layer. Finally, C-terminal GFP fusion proteins for At1g74450 were shown to localise to the cytosol.
Highlights
IntroductionPlants depend on their ability to coordinate growth and development with environmental conditions [1]
As sessile organisms, plants depend on their ability to coordinate growth and development with environmental conditions [1]
RT-PCR results showed that the five homozygous T-DNA insertion lines are all knockout lines (Fig 1)
Summary
Plants depend on their ability to coordinate growth and development with environmental conditions [1]. The balance between tolerance and sensitivity in particular plant species may determine whether a stress factor has positive (eustress) or negative effects [3]. In model plants like Arabidopsis thaliana, tolerance is often measured as “survival”, whilst in crop species like cereals, maintenance of “yield” and “productivity” is for economic reasons more important than survival [4]. Whilst some stress regulated genes in plants are differentially expressed in response to particular stress factors, others react to a broad spectrum of adverse environmental conditions. These 197 genes appear to represent a common or universal stress response transcriptome, since many of the genes are conserved among plants, animals and fungi and are stress regulated in all organisms. The timing of expression of these genes can be early: within 45 minutes of exposure to abiotic stress, the expression of several multiple-stress responsive genes in Arabidopsis was found to be significantly up-regulated [7]
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