Biology subjects

Heidari, B.

Publications and source records attributed to Heidari, B..

3 recordsLinked to original sources

bioRxiv2026

Chlorophyll binding to Cytochrome b6f precedes photosystem I and II in barley etioplasts

Chlorophyll (Chl) is essential for oxygenic photosynthesis, binding to membrane proteins for light harvesting and electron transfer. In angiosperms, Chl synthesis is halted in darkness, preventing accumulation of Chl-binding photosynthetic complexes in etioplasts. However, etioplasts assemble a dimeric Cytochrome b6f (Cyt b6f) complex, uniquely binding protochlorophyll (Pchl), the esterified derivative of protochlorophyllide (Pchlide). This indicates an evolutionarily conserved structural or functional role for Pchl distinct from the Chl bound in Cyt b6f in chloroplasts. Here we show that upon light-induced Chl synthesis in-vivo and in-vitro, Chl accumulation in Cyt b6f dimers precedes photosystems I and II. We find that chlorophyllide and Chl bind to the light-harvesting-like protein 3 (LIL3), supporting a role for LIL3 in early Chl allocation that extends its described role in stabilizing geranylgeranyl reductase. We determine a dissociation constant of 246.6 {+/-} 37 nM for Chlide binding to LIL3 in-vitro and show that Cyt b6f monomers and LIL3 co-migrate with Chlide in native PAGE, whereas Cyt b6f dimers and LIL3 co-migrate with Chl. These results indicate that Chlide binding to LIL3 chaperones esterification to Chl and reduction of geranylgeraniol, and that Chl release with Cyt b6f dimerization prioritizes Chl binding to Cyt b6f assembly during de-etiolation.

plant biology↗

bioRxiv2020

An amplified derepression controller with multisite inhibition and positive feedback

How organisms are able to maintain robust homeostasis has in recent years received increased attention by the use of combined control engineering and kinetic concepts, which led to the discovery of robust controller motifs. While these motifs employ kinetic conditions showing integral feedback and homeostasis for step-wise perturbations, the motifs performance differ significantly when exposing them to time dependent perturbations. One type of controller motifs which are able to handle exponentially and even hyperbolically growing perturbations are based on derepression. In these controllers the compensatory reaction, which neutralizes the perturbation, is derepressed, i.e. its reaction rate is increased by the decrease of an inhibitor acting on the compensatory flux. While controllers in this category can deal well with different time-dependent perturbations they have the disadvantage that they break down once the concentration of the regulatory inhibitor becomes too low and the compensatory flux has gained its maximum value. We wondered whether it would be possible to bypass this restriction, while still keeping the advantages of derepression kinetics. In this paper we show how the inclusion of multisite inhibition and the presence of positive feedback loops lead to an amplified controller which is still based on derepression kinetics but without showing the breakdown due to low inhibitor concentrations. By searching for the amplified feedback motif in natural systems, we found it as a part of the plant circadian clock where it is highly interlocked with other feedback loops.

systems biology↗

bioRxiv2020

Analysis of genetic diversity and association of seed and mucilage yields with inter simple sequence repeats (ISSR) polymorphism in a collection of Plantgao species

Analysis of genetic diversity in medicinal plants assists germplasm conservation and selection for use in breeding schemes. The aims of the present study were to assess genetic diversity and differentiation of several Plantago species using Inter Simple Sequence Repeats (ISSR) markers and identify marker-trait associations (MTAs). Thirty-one Plantago accessions belonging to eight species with various mating system and chromosome number were collected from geographical regions of Iran environments. Polymorphism in the DNA of Plantago accessions were analyzed using polymerase chain reaction (PCR) of 25 ISSR primers. The data for number of polymorphic bands were analyzed on the basis of several genetic diversity parameters. The results of gel analysis indicated that the ISSR primers amplified 5 to 21 polymorphic bands with 100 to 3000 bp size. The mean polymorphism was 83.83% and five primers showed 100% polymorphism among Plantago accessions. The Polymorphism Information Content (PIC) for ISSR as a dominant marker ranged from 0.1103 to 0.3829 with the mean 0.2727 in the species tested. Accessions in P. amplexicaulis and P. pysillum species represented the highest Neis and Shannons genetic diversity whilst the lowest obtained for P. lagopus. Analysis of phylogenetic network generated by the Neighbor-Net Algorithm showed moderate split of the eight species tested and the network depicted moderate conflict. The principal coordinate analysis (PCoA) results showed lower conflict in separation of accessions of the eight species. Fifty-six significant MTAs were detected for the traits tested in Plantago accessions, of which six were shared between three seed and mucilage traits and 24 were common between two traits. The coefficient of determination (R2) for the identified MTAs varied between 32 and 73%. In conclusion, the results of genetic diversity analysis suggested that ISSR marker could efficiently differentiate Plantago species and the information of genetic diversity might assist Plantago improvement and conservation.

plant biology↗