The N-region sequence context impacts the chloroplast import efficiency of multi-TMD protein.

Targeting heterologous multi-transmembrane domain (TMD) proteins to plant chloroplasts requires sequences in addition to the chloroplast transit peptide (cTP). The N-terminal domain (N-region), located C-terminal to the cTP in chloroplast inner envelope membrane proteins, is an essential region for import. However, it was unclear if the N-region functions solely as a spacer sequence to facilitate cTP access or if it plays an active role in the import process. This study addresses the N-region's role by using combinations of cTPs and N-regions from Arabidopsis chloroplast inner envelope membrane proteins to direct the cyanobacterial protein SbtA to the chloroplast. We find that the sequence context of the N-region affects the chloroplast import efficiency of SbtA, with particular sequences mis-targeting the protein to different cellular sub-compartments. Additionally, specific cTP and N-region pairs exhibit varying targeting efficiencies for different heterologous proteins. Substituting individual N-region motifs did not significantly alter the chloroplast targeting efficiency of a particular cTP and N-region pair. We conclude that the N-region exhibits contextual functioning and potentially functional redundancy in motifs.

Artificially designed synthetic promoter for a high level of salt induction using a cis-engineering approach.

This work aimed to design a synthetic salt-inducible promoter using a cis-engineering approach. The designed promoter (PS) comprises a minimal promoter sequence for basal-level expression and upstream cis-regulatory elements (CREs) from promoters of salinity-stress-induced genes. The copy number, spacer lengths, and locations of CREs were manually determined based on their occurrence within native promoters. The initial activity profile of the synthesized PS promoter in transiently transformed N. tabacum leaves shows a seven-fold, five-fold, and four-fold increase in reporter GUS activity under salt, drought, and abscisic acid stress, respectively, at the 24-h interval, compared to the constitutive CaMV35S promoter. Analysis of gus expression in stable Arabidopsis transformants showed that the PS promoter induces over a two-fold increase in expression under drought or abscisic acid stress and a five-fold increase under salt stress at 24- and 48-h intervals, compared to the CaMV35S promoter. The promoter PS exhibits higher and more sustained activity under salt, drought, and abscisic acid stress compared to the constitutive CaMV35S.

Insight into strigolactone hormone functions in plant parasitic weeds: a regulatory perspective

The strigolactones (SLs) are plants hormones that have multiple functions in architecture and development. The roles of SLs in shoot branching and stem secondary growth of autotrophic plants are established. SL is also involved in the interaction between root parasitic plants and their host plants. SLs are exudates by the root of the host plant in search of a fungal partner for symbiotic association, while parasitic plants utilize this facility to detect the host root. The first formed tubercle of Philapanhche, whose germinations are driven by host-derived SLs, exudates parasitic derived SLs (PSLs) and could encourages germination of the adjacent parasitic seeds, resulting in parasite cluster formation. The existence of aboveground spikes in clusters suggests an intriguing approach for increasing parasite population by amplifying PSLs, which result in massive parasitic seed germination. PSLs probably have a role in the increased branching of Broomrapes opposing the host plant, resulting in the parasites' clustered appearance aboveground. This review highlights the distinct roles of SLs and PSLs, and their potential role in host-parasitic interaction.