Biology subjects

Hardtke, C.

Publications and source records attributed to Hardtke, C..

3 recordsLinked to original sources

bioRxiv2022

Heterologous expression of a lycophyte protein enhances angiosperm seedling vigor

Seedling vigor is a key agronomic trait that determines juvenile plant performance. Angiosperm seeds develop inside fruits and are connected to the mother plant through vascular tissues. Their formation requires plant-specific genes, such as BREVIS RADIX (BRX) in Arabidopsis thaliana roots. BRX family proteins are found throughout the angiosperms but also occur in non-vascular bryophytes and non-seed lycophytes. They consist of four conserved domains, including the tandem "BRX-domains". We found that bryophyte or lycophyte BRX homologs can only partially substitute for Arabidopsis BRX (AtBRX) because they miss key features in the linker between the BRX-domains. Intriguingly however, expression of a BRX homolog from the lycophyte Selaginella moellendorffii (SmBRX) in A. thaliana wildtype background confers robustly enhanced root growth vigor that persists throughout the life cycle. This effect can be traced back to a substantial increase in seed and embryo size, and can be reproduced with a modified, "SmBRX-like" variant of AtBRX. Our results thus suggest that BRX variants could serve as biotechnological tools to boost seedling vigor and shed light on the activity of ancient, non-angiosperm BRX family proteins.

plant biology↗

bioRxiv2021

Metaphloem development in the Arabidopsis root tip

The phloem transport network is a major evolutionary innovation that enabled plants to dominate terrestrial ecosystems. In the growth apices, the meristems, apical stem cells continuously produce early, so-called protophloem. This is easily observed in Arabidopsis root meristems, where the differentiation of individual protophloem sieve element precursors into interconnected, conducting sieve tubes is laid out in a spatio-temporal gradient. The mature protophloem eventually collapses as the neighboring metaphloem takes over its function further distal from the stem cell niche. Compared to protophloem, metaphloem ontogenesis is poorly characterized, primarily because its visualization is challenging. Here we describe an improved protocol to investigate metaphloem development in Arabidopsis root tips in combination with a set of new molecular markers. We found that mature metaphloem sieve elements are only observed in the late post-meristematic root although their specification is initiated as soon as protophloem sieve elements enucleate. Moreover, unlike protophloem sieve elements, metaphloem sieve elements only differentiate once they have fully elongated. Finally, our results suggest that metaphloem differentiation is not directly controlled by protophloem-derived cues but rather follows a distinct, robust developmental trajectory. Summary statementMetaphloem sieve element differentiation in Arabidopsis roots follows a robust developmental trajectory.

plant biology↗

bioRxiv2021

A conserved regulatory module regulates receptor kinase signaling in immunity and development

Ligand recognition by cell-surface receptors underlies development and immunity in both animals and plants. Modulating receptor signaling is critical for appropriate cellular responses but the mechanisms ensuring this are poorly understood. Here, we show that signaling by plant receptors for pathogen-associated molecular patterns (PAMPs) in immunity and CLAVATA3/EMBRYO SURROUNDING REGION-RELATED peptides (CLEp) in development employ a similar regulatory module. In the absence of ligand, signaling is dampened through association with specific type-2C protein phosphatases (PP2Cs). Upon activation, PAMP and CLEp receptors phosphorylate divergent cytosolic kinases, which, in turn, phosphorylate the phosphatases, thereby promoting their release from the receptor complexes. Our work reveals a regulatory circuit shared between immune and developmental receptor signaling, which may have broader important implications for plant receptor kinase-mediated signaling in general.

plant biology↗