Tuning a timing device that regulates lateral root development in rice

Abstract

Peptidyl Prolyl Isomerases (PPIases) accelerate cis-trans isomerization of prolyl peptide bonds. In rice, the PPIase LRT2 is essential for lateral root initiation. LRT2 displays in vitro isomerization of a highly conserved W-P peptide bond ( 104 W-P 105 ) in the natural substrate OsIAA11. OsIAA11 is a transcription repressor that, in response to the plant hormone auxin, is targeted to ubiquitinmediated proteasomal degradation via specific recognition of the cis isomer of its 104 W-P 105 peptide bond. OsIAA11 controls transcription of specific genes, including its own, that are required for lateral root development. This auxin-responsive negative feedback circuit governs patterning and development of lateral roots along the primary root. The ability to tune LRT2 activity via mutagenesis is crucial for understanding and modeling the role of this bimodal switch in the auxin circuit and lateral root development. We present characterization of the thermal stability and isomerization rates of several LRT2 mutants acting on the OsIAA11 substrate. The thermally stable mutants display activities lower than that of wild-type (WT) LRT2. These include binding diminished but catalytically active P125K, binding incompetent W128A, and binding capable but catalytically incompetent H133Q mutations. Additionally, LRT2 homologs hCypA from human, TaCypA from Triticum aestivum (wheat) and PPIB from E. coli were shown to have 110%, 50% and 60% of WT LRT2 activity on the OsIAA11 substrate. These studies identify several thermally stable LRT2 mutants with altered activities that will be useful for establishing relationships between cis-trans isomerization, auxin circuit dynamics, and lateral root development in rice.

Encapsulation of bioactive compounds extracted from haritaki pulp (Terminalia chebula Retzius): characterization of physical, thermal, and morphological properties

“…Previous studies suggest that the first stage of weight loss is similar to the physical dehydration of starch, while the second stage entailed chemical and thermal degradation. 54 At the third stage, chemical oxidation caused weight loss, which resulted in varied mass losses at temperatures between 300 and 400 °C. This stage, which is a combustion stage, is what completely oxidised the organic materials.…”

Improvement in pasting, thermal properties, and in vitro digestibility of isolated Amaranth starch ( Amaranthus cruentus L.) by addition of almond gum and gum ghatti powder

“…Bet et al (2018) reported the 7.8% loss in the first stage is concordant to the native starch, but incorporation of gum has significantly influenced the mass loss. According to prior report, the first stage of weight loss resembled physical dehydration of starch, whereas the second stage involved chemical dehydration as well as thermal decomposition (Acevedo et al, 2019). The second stage weight loss appeared at temperature ranges of 230-350°C, and this loss varied from 40% to 47.42% and 4.31% to 48.41% for variable compositions of SAG and SGG.…”