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21.
22.
Accurate prediction of the leaching requirements (Lr) of crops and striving to attain them is essential for efficient irrigation
water use. Solute modeling was extended to develop four Lr conceptual models that do not neglect solute reactions in the root-zone,
surface evaporation, and the influence of immobile wetted pore space. The models were based on: (i) the water movement equation
which included an exponential water-uptake function (-e) or the 40-30-20-10 water-uptake function (-4); (ii) the solute movement
equation for a reactive salt of a linear reaction term (the Lrchem-e and Lrchem-4 models); or the employment of output (salinity
of soil solution, EC vs concentration factor, CF) of the SAO comprehensive chemical model (the LrSAO-e and LrSAO-4 models);
and (iii) the inclusion of an effective soil solution volume in the transport equations. The root-zone average relative effective
soil solution volume νeff (L | L50, p) was of sigmoidal response to leaching fraction (L) with two adjustable parameters L50
and p; the root-zone average reduced retention coefficient decreased linearly with L; and salt concentration at soil surface
was related to salt concentration of irrigation water (ECi) by the fraction of irrigation water that evaporated (∈). The resulted
concentration profiles indicated the salt behaved as a conservative one down to a threshold depth (xs) below of which salt
was retained and precipitated. The depth of the conservative-salt front, xs increased with L and the 40-30-20-10 water-uptake
pattern overestimated the xs depth relative to the exponential pattern. Concentration profiles were integrated to compute
the root-zone average salinity, which was converted to crop salt-tolerance threshold (AE). The four conceptual models were
successfully calibrated using experimental AE/ECi vs. Lr data with the input parameter values: ς = 0.27, p = 1.44, L50 = 0.16,
ω = 2, and ∈ = 0 or 0.1 for the exponential or the 40-30-20-10 pattern, respectively; where ς is relative root length parameter
and ω is a weighing parameter. No significant difference existed between the four model correlations at the 0.05 level. The
four models require ECi and AE of the crop as input for Lr prediction. Sensitivity analysis revealed predicted Lr was sensitive
the least to error in ∈. For tolerant and moderately tolerant crops Lr was sensitive the most to ς, and for sensitive crops
to L50 and p. Model verification and validation were discussed. In deriving the present Lr models, no osmotic adjustment was
required and both the exponential and the 40-30-20-10 water uptake patterns were, equivalently, applicable.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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《Journal of molecular biology》2021,433(3):166757
Regulation of bacterial stress responding σS is a sophisticated process and mediated by multiple interacting partners. Controlled proteolysis of σS is regulated by RssB which maintains minimal level of σS during exponential growth but then elevates σS level while facing stresses. Bacteria developed different strategies to regulate activity of RssB, including phosphorylation of itself and production of anti-adaptors. However, the function of phosphorylation is controversial and the mechanism of anti-adaptors preventing RssB-σS interaction remains elusive. Here, we demonstrated the impact of phosphorylation on the activity of RssB and built the RssB-σS complex model. Importantly, we showed that the phosphorylation site - D58 is at the interface of RssB-σS complex. Hence, mutation or phosphorylation of D58 would weaken the interaction of RssB with σS. We found that the anti-adaptor protein IraD has higher affinity than σS to RssB and its binding interface on RssB overlaps with that for σS. And IraD-RssB complex is preferred over RssB-σS in solution, regardless of the phosphorylation state of RssB. Our study suggests that RssB possesses a two-tier mechanism for regulating σS. First, phosphorylation of RssB provides a moderate and reversible tempering of its activity, followed by a specific and robust inhibition via the anti-adaptor interaction. 相似文献
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Man Lung Yeung Jade Lee Lee Teng Lilong Jia Chaoyu Zhang Chengxi Huang Jian-Piao Cai Runhong Zhou Kwok-Hung Chan Hanjun Zhao Lin Zhu Kam-Leung Siu Sin-Yee Fung Susan Yung Tak Mao Chan Kelvin Kai-Wang To Jasper Fuk-Woo Chan Zongwei Cai Susanna Kar Pui Lau Kwok-Yung Yuen 《Cell》2021,184(8):2212-2228.e12
28.
Olivia Sveidahl Johansen Tao Ma Jakob Bondo Hansen Lasse Kruse Markussen Renate Schreiber Laia Reverte-Salisa Hua Dong Dan Ploug Christensen Wenfei Sun Thorsten Gnad Iuliia Karavaeva Thomas Svava Nielsen Sander Kooijman Cheryl Cero Oksana Dmytriyeva Yachen Shen Maria Razzoli Shannon L. O’Brien Zachary Gerhart-Hines 《Cell》2021,184(13):3502-3518.e33
29.
《Journal of molecular biology》2021,433(21):167223
Most eukaryotic transmembrane and secreted proteins contain N-terminal signal peptides that mediate insertion of the nascent translation products into the membrane of the endoplasmic reticulum. After membrane insertion, signal peptides typically are cleaved from the mature protein and degraded. Here, we tested whether a small hydrophobic protein selected for growth promoting activity in mammalian cells retained transforming activity while also acting as a signal peptide. We replaced the signal peptide of the PDGF β receptor (PDGFβR) with a previously described 29-residue artificial transmembrane protein named 9C3 that can activate the PDGFβR in trans. We showed that a modified version of 9C3 at the N-terminus of the PDGFβR can function as a signal peptide, as assessed by its ability to support high level expression, glycosylation, and cell surface localization of the PDGFβR. The 9C3 signal peptide retains its ability to interact with the transmembrane domain of the PDGFβR and cause receptor activation and cell proliferation. Cleavage of the 9C3 signal peptide from the mature receptor is not required for these activities. However, signal peptide cleavage does occur in some molecules, and the cleaved signal peptide can persist in cells and activate a co-expressed PDGFβR in trans. Our finding that a hydrophobic sequence can display signal peptide and transforming activity suggest that some naturally occurring signal peptides may also display additional biological activities by interacting with the transmembrane domains of target proteins. 相似文献
30.