Cuticular Lipid Composition, Surface Structure, and Gene Expression in Arabidopsis Stem Epidermis

Abstract

All vascular plants are protected from the environment by a cuticle, a lipophilic layer synthesized by epidermal cells and composed of a cutin polymer matrix and waxes. The mechanism by which epidermal cells accumulate and assemble cuticle components in rapidly expanding organs is largely unknown. We have begun to address this question by analyzing the lipid compositional variance, the surface micromorphology, and the transcriptome of epidermal cells in elongating Arabidopsis (Arabidopsis thaliana) stems. The rate of cell elongation is maximal near the apical meristem and decreases steeply toward the middle of the stem, where it is 10 times slower. During and after this elongation, the cuticular wax load and composition remain remarkably constant (32 mg/cm 2 ), indicating that the biosynthetic flux into waxes is closely matched to surface area expansion. By contrast, the load of polyester monomers per unit surface area decreases more than 2-fold from the upper (8 mg/cm 2 ) to the lower (3 mg/cm 2 ) portion of the stem, although the compositional variance is minor. To aid identification of proteins involved in the biosynthesis of waxes and cutin, we have isolated epidermal peels from Arabidopsis stems and determined transcript profiles in both rapidly expanding and nonexpanding cells. This transcriptome analysis was validated by the correct classification of known epidermis-specific genes. The 15% transcripts preferentially expressed in the epidermis were enriched in genes encoding proteins predicted to be membrane associated and involved in lipid metabolism. An analysis of the lipid-related subset is presented.

Unique and Overlapping Expression Patterns among Members of Photosynthesis-Associated Nuclear Gene Families in Arabidopsis

“…Furthermore, abundance of RbcS and Lhc transcripts can be regulated at the posttranscriptional level (Tobin and Silverthorne, 1985;Simpson and Herrera-Estrella, 1990;Thompson and White, 1991). However, our results are in good agreement with Arabidopsis RbcS and Lhc expression profiles reported previously (Dedonder et al, 1993;Klimmek et al, 2006) or extracted from publicly accessible large-scale microarray data sets (Birnbaum et al, 2003;Leonhardt et al, 2004;Schmid et al, 2005;Suh et al, 2005;Winter et al, 2007;Supplemental Table S3; Supplemental Fig. S9; and below), suggesting that, at least in Arabidopsis, cellular dynamics of RbcS and Lhc expression are largely determined by transcription patterns.…”

Developmentally equivalent tissue sampling based on growth kinematic profiling of Arabidopsis inflorescence stems

“…Manual measurement of the rates of separation of ink marks positioned 5 mm apart along the Arabidopsis inflorescence stem, relative to the base of the stem, did establish that no elongative growth occurred at distances > 7 cm below the apex of the stem in Columbia (Col-0) plants over a 24 h period, which made it possible to contrast pre-vs post-cessation states (Suh et al, 2005). These samples were presumed to broadly represent growth stages involving predominantly primary and secondary cell wall formation, respectively, but this approach of tracking ink mark movement cannot isolate regions of maximum tissue expansion rate.…”

On the role of a Lipid-Transfer Protein. Arabidopsis ltp3 mutant is compromised in germination and seedling growth.

“…21 Other LTPs can also function in cuticle synthesis which correlates with a role in biotic and abiotic stress tolerance through reinforcement of this mechanical barrier which, in turn, prevents pathogen entry and reduces water losses. [22][23] On the other hand, a LTP from tobacco was shown to promote cell wall loosening and may play a role in cell expansion and consequently in plant growth. 24 Besides, the LTP SCA from lily styles is required for pollen tube adhesion.…”