Role of temperature in regulating the timing of germination in Portulaca oleracea

The peak of germination of autumn-sown seeds of Portulaca oleracea was between 21 May and 21 June, when mean daily maximum and minimum temperatures were 30.7 and 17.4 °C, respectively. Fresh seeds collected in October germinated to 13 and 94% at 30:15 and 35:20 °C thermoperiods, respectively, in light, and to 0% in darkness. Seeds were buried in October 1975 and exhumed in December 1975 through September 1976. In light, exhumed seeds germinated to 69–100% at 30:15 and 35:20 °C,to 1–80% at 20:10 °C, and to 0–52% at 15:6 °C; in darkness they germinated to 5–55% at 30:15 and 35:20 °C and to0% at 20:10 and 15:6 °C. Germination at 20:10 °C did not exceed 50% until mid-April, and it did not exceed 50% at 15:6 °C until June. Fresh seeds were buried at 5, 15:6, 20:10, 25:15, 30:15, and 35:20 °C, and after 0, 1, 3, and 5 months, seeds from each temperature were tested in light and darkness at the five thermoperiods. The minimum temperature at which 50% or more of the seeds germinated in light decreased with an increase in afterripening temperature. The high temperature requirement for complete afterripening and for germination of partially afterripened seeds prevents germination of this summer annual in temperate regions until late spring and early summer.

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The crystal structure of Mycobacterium tuberculosis high-temperature requirement A protein reveals an autoregulatory mechanism

Acta Crystallographica Section F Structural Biology Communications ◽

10.1107/s2053230x18016217 ◽

2018 ◽

Vol 74 (12) ◽

pp. 803-809

Author(s):

Arvind Kumar Gupta ◽

Debashree Behera ◽

Balasubramanian Gopal

Keyword(s):

Crystal Structure ◽

Mycobacterium Tuberculosis ◽

High Temperature ◽

Catalytic Domain ◽

Pdz Domain ◽

Regulatory Pathways ◽

Inactive Conformation ◽

Temperature Requirement ◽

Autoregulatory Mechanism

The crystal structure of Mycobacterium tuberculosis high-temperature requirement A (HtrA) protein was determined at 1.83 Å resolution. This membrane-associated protease is essential for the survival of M. tuberculosis. The crystal structure reveals that interactions between the PDZ domain and the catalytic domain in HtrA lead to an inactive conformation. This finding is consistent with its proposed role as a regulatory protease that is conditionally activated upon appropriate environmental triggers. The structure provides a basis for directed studies to evaluate the role of this essential protein and the regulatory pathways that are influenced by this protease.

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High temperature requirement A1 in cancer: biomarker and therapeutic target

Cancer Cell International ◽

10.1186/s12935-021-02203-4 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Mingming Chen ◽

Shilei Yang ◽

Yu Wu ◽

Zirui Zhao ◽

Xiaohan Zhai ◽

...

Keyword(s):

High Temperature ◽

Therapeutic Target ◽

Public Health Problem ◽

Diagnostic Biomarkers ◽

Temperature Requirement ◽

Incidence And Mortality ◽

A Cell ◽

Cell Type Specific ◽

Cancer Types

AbstractAs the life expectancy of the population increases worldwide, cancer is becoming a substantial public health problem. Considering its recurrence and mortality rates, most cancer cases are difficult to cure. In recent decades, a large number of studies have been carried out on different cancer types; unfortunately, tumor incidence and mortality have not been effectively improved. At present, early diagnostic biomarkers and accurate therapeutic strategies for cancer are lacking. High temperature requirement A1 (HtrA1) is a trypsin-fold serine protease that is also a chymotrypsin-like protease family member originally discovered in bacteria and later discovered in mammalian systems. HtrA1 gene expression is decreased in diverse cancers, and it may play a role as a tumor suppressor for promoting the death of tumor cells. This work aimed to examine the role of HtrA1 as a cell type-specific diagnostic biomarker or as an internal and external regulatory factor of diverse cancers. The findings of this study will facilitate the development of HtrA1 as a therapeutic target.

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Molecular structure and the role of high‐temperature requirement protein 1 in skeletal disorders and cancers

Cell Proliferation ◽

10.1111/cpr.12746 ◽

2019 ◽

Vol 53 (2) ◽

Cited By ~ 1

Author(s):

Yihe Li ◽

Jinbo Yuan ◽

Emel Rothzerg ◽

Xinghuo Wu ◽

Huazi Xu ◽

...

Keyword(s):

Molecular Structure ◽

High Temperature ◽

Temperature Requirement ◽

Skeletal Disorders

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Role of dispersal date and changes in physiological responses in controlling timing of germination in achenes of Geum canadense

Canadian Journal of Botany ◽

10.1139/b85-227 ◽

1985 ◽

Vol 63 (9) ◽

pp. 1654-1658 ◽

Cited By ~ 8

Author(s):

Jerry M. Baskin ◽

Carol C. Baskin

Keyword(s):

High Temperatures ◽

Low Temperatures ◽

Physiological Responses ◽

Early Spring ◽

Early Summer ◽

Test Conditions ◽

Temperature Requirement ◽

Before And After ◽

Germination Requirements

This study examines the importance of the date of dispersal, and of the changes in the physiological responses of achenes before and after dispersal, in regulating timing of germination in Geum canadense Jacq. The effect of dispersal date on germination was tested by collecting achenes from the parent plants from September through June and sowing them on soil in an unheated greenhouse. Changes in germination responses were monitored by testing achenes of each collection in light and darkness over a range of thermoperiods. Regardless of test conditions, achenes required light for germination. At maturity in September, 90% of the achenes germinated at the September thermoperiod (30:15 °C (maximum:minimum)), but none germinated in November at the November thermoperiod (15:6 °C). Achenes sown in September germinated that autumn and the following spring, but none of those sown in November germinated until spring. As achenes overwintered on plants in the field, germination percentages decreased at 20:10, 25:15, and 30:15 °C and increased at 15:6 and 5 °C. Thus, achenes sown in early spring germinated immediately, while those sown in early summer did not germinate until later. Germination requirements of the achenes also changed after dispersal. Stratification lowered the temperature requirement for germination, and thus achenes sown in autumn germinated in March at temperatures that had inhibited germination in the autumn. Achenes dispersed in May and June did not regain the ability to germinate at high temperatures during summer, and they lost the ability to germinate at low temperatures. Therefore, most of these latter achenes did not germinate until the following spring, after they had been stratified during the winter.

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Dissecting the role of interprotomer cooperativity in the activation of oligomeric high-temperature requirement A2 protein

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2111257118 ◽

2021 ◽

Vol 118 (35) ◽

pp. e2111257118

Author(s):

Yuki Toyama ◽

Robert W. Harkness ◽

Lewis E. Kay

Keyword(s):

High Temperature ◽

Ligand Binding ◽

Pdz Domain ◽

Nmr Studies ◽

Transverse Relaxation ◽

Temperature Requirement ◽

Biochemical Assays ◽

Substrate Concentrations ◽

Binding Substrate

The human high-temperature requirement A2 (HtrA2) mitochondrial protease is critical for cellular proteostasis, with mutations in this enzyme closely associated with the onset of neurodegenerative disorders. HtrA2 forms a homotrimeric structure, with each subunit composed of protease and PDZ (PSD-95, DLG, ZO-1) domains. Although we had previously shown that successive ligand binding occurs with increasing affinity, and it has been suggested that allostery plays a role in regulating catalysis, the molecular details of how this occurs have not been established. Here, we use cysteine-based chemistry to generate subunits in different conformational states along with a protomer mixing strategy, biochemical assays, and methyl-transverse relaxation optimized spectroscopy–based NMR studies to understand the role of interprotomer allostery in regulating HtrA2 function. We show that substrate binding to a PDZ domain of one protomer increases millisecond-to-microsecond timescale dynamics in neighboring subunits that prime them for binding substrate molecules. Only when all three PDZ-binding sites are substrate bound can the enzyme transition into an active conformation that involves significant structural rearrangements of the protease domains. Our results thus explain why when one (or more) of the protomers is fixed in a ligand-binding–incompetent conformation or contains the inactivating S276C mutation that is causative for a neurodegenerative phenotype in mouse models of Parkinson’s disease, transition to an active state cannot be formed. In this manner, wild-type HtrA2 is only active when substrate concentrations are high and therefore toxic and unregulated proteolysis of nonsubstrate proteins can be suppressed.

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