Tracking transience: a method for dynamic monitoring of biological events in Arabidopsis thaliana biosensors

Plant Nanobionics: Application of Nanobiosensors in Plant Biology

Nanobiosensors (NBSs) are a class of chemical sensors which are sensitive to a physical or chemical stimulus (heat, acidity, metabolism transformations) that conveys information about vital processes. NBSs detect physiological signals and convert them into standardized signals, often electrical, to be quantified from analog to digital. NBSs are classified according to the transducer element (electrochemical, piezoelectric, optical, and thermal) in accordance with biorecognition principle (enzyme recognition, affinity immunoassay, whole sensors, DNA). NBSs have varied forms, depending on the degree of interpretation of natural processes in plants. Plant nanobionics uses mathematical models based on qualitative and less quantitative records. NBSs can give information about endogenous concentrations or endogenous fluxes of signaling molecules (phytohormones). The properties of NBSs are temporal and spatial resolution, the ability of being used without significantly interfering with the system. NBSs with the best properties are the optically genetically coded NBSs, but each NBS needs specific development efforts. NBS technologies using antibodies as a recognition domain are generic and tend to be more invasive, and there are examples of their use in plant nanobionics. Through opportunities that develop along with technologies, we hope that more and more NBSs will become available for plant nanobionics. The main advantages of NBSs are short analysis time, low-cost tests and portability, real-time measurements, and remote control.

Longitudinal patterning in roots: a GATA2-auxin interaction underlies and maintains the root transition domain

In Arabidopsis thaliana root meristems the GATA2 transcription factor is a marker for the root transition domain, is auxin regulated, and functions to restrict cell division activity. The growing part of roots is comprised of three discrete regions; the proliferative domain (PD), an elongation zone, and interposed between these two, the transition domain (TD), which is the focus of this investigation. Within the TD, it is hypothesized that cells are reprogrammed, losing the capacity to divide and begin to differentiate. In recently germinated Arabidopsis thaliana seedlings, a TD is not anatomically evident, but subsequently forms in a region of the root in which there has occurred prior expression of both AUX1/PIN2 proteins and of transcripts of the GATA transcription factor family (pGATA2:H2B-YFP or pGATA2:GUS). pGATA2:GUS expression is regulated by auxin and is reduced in seedlings in which either auxin transport or auxin sensitivity is perturbed. Application of cytokinin results in a reduction in both pGATA2:GUS expression and in TD cell number, via a pathway involving ARR1 and ARR12. Overexpression of GATA2 is accompanied by a reduction in cell number in the PD, but has no effect on cell number in the TD, whereas in knockdowns of GATA transcription factors, cell number is reduced in both the PD and TD. We conclude: (1) that GATA2 expression is localized to (a marker for) the TD; (2) that development and maintenance of the TD are associated with an auxin-regulation of GATA2 expression; (3) that GATA transcription factors function to restrict cell division activity.