Study on the extremely cold winter of 1670 over the middle and lower reaches of the Yangtze River

The snow-cover days over the middle and lower reaches of the Yangtze River （MLRYR） in the winter of 1670 were extracted from Chinese historical documents. By these records, the winter temperature anomalies （compared to the mean of 1961-1990） recorded at seven meteorological stations and the regional mean winter temperature were estimated. The results show that： （1） There was an average of about 30 snow-cover days over the MLRYR region in 1670, ranging from 11-20 days in Shanghai and eastern Zhejiang to 5140 days in eastern Hunan Province. The snow-cover days averaged about 40 days in Anqing and Nan- cheng, and ranged from 30 to 40 days in Quzhou, Jingdezhen, and Nanchang; and （2） the regional mean winter temperature in 1670 was estimated to be approximately 4.0 ℃ lower than that of 1961-1990. The maximum negative anomaly of 5.6℃ occurred in Nanchang and the minimum anomaly of-2.8 ℃ was detected in Quzhou. Both of these were lower than that of the coldest winter during the instrumental observation period of 1951-2010. This research could not only provide a method to es- timate historical climate extremes, but also provide a background to understand the recent instrumentally climate extremes.

Phytosulfokine-α Promotes Root Growth by Repressing Expression of Pectin Methylesterase Inhibitor (PMEI) Genes in Medicago truncatula

Phytosulfokine-α(PSK-α),a sulfated pentapeptide with the sequence YIYTQ,is encoded by a small precursor gene family in Arabidopsis.PSK-αregulates multiple growth and developmental processes as a novel peptide hormone.Despite its importance,functions of PSK-αin M.truncatula growth remains unknown.In this study,we identified five genes to encode PSK-αprecursors in M.truncatula.All of these precursors possess conserved PSK-αsignature motif.Expression pattern analysis of these MtPSK genes revealed that each gene was expressed in a tissue-specific or ubiquitous pattern and three of them were remarkably expressed in root.Treatment of M.truncatula seedlings with synthetic PSK-αpeptide significantly promoted root elongation.In addition,expression analysis of downstream genes by RNA-seq and qRT-PCR assays suggested that PSK-αsignaling might regulate cell wall structure via PMEI-PME module to promote root cell growth.Taken together,our results shed light on the mechanism by which PSK-αpromotes root growth in M.truncatula,providing a new resource for improvement of root growth in agriculture.

Reconstruction of Sub-Decadal Winter Half-Year Temperature during 1651-2010 for the North China Plain Using Records of Frost Date

We extracted 374 pieces of records of frost date from historical documents. Using these records, we reconstructed winter half-year (October to next April) temperature series, with a resolution of 5-year, for the North China Plain during 1651-2010. The results show that the temperature changes in the North China Plain were divided into four phases. With the reference period of 1951-1980, two cold phases, 1651-1700 and 1781-1900, have cold anomaly of 0.83°C and 0.60°C respectively. However, between the two cold phases, 1701-1780 was a relative warm phase with the cold anomaly of 0.36°C referring to the mean of 1951-1980. After the 1900, the climate came into a warm phase. The mean temperature of 1901-2010 was 0.11°C higher than the mean of 1951-1980. During 1651-2010, the 1996-2000 is the warmest 5-year with the warm anomaly of 1.25°C than that of the reference period of 1951-1980.

Late Holocene brGDGTs-based quantitative paleotemperature reconstruction from lacustrine sediments on the western Tibetan Plateau

We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃ at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.

The MtRGF6 Peptide Differentially Regulates Root Development and Symbiotic Nodulation of Medicago truncatula and Lotus japonicus

Rhizobia induces nitrogen-fixing nodules in legumes used in agricultural production,providing a direct source of combined nitrogen to leguminous crops.Small peptides,such as CLAVATA3/EMBRYO SURROUNDING REGION peptides(CLE),are known to regulate the formation and development of nitrogen-fixing nodules in legumes.Root meristem growth factor(RGF)peptides from Medicago truncatula not only regulate root develop-ment but also modulate nodulation symbiosis with Sinorhizobium meliloti.However,the impact of RGF peptides from one leguminous species on the others remains unclear.In this study,we investigate the effects of the RGF family peptide MtRGF6p from M.truncatula on nodulation symbiosis and root development in Lotus japonicus.The MtRGF6 gene is predominantly expressed in the root nodules of M.truncatula and shows low identity with RGF homologous genes from L.japonicus.The gene promoter is active in the primordia of root nodules and lat-eral roots,as well as in young nodules and roots,and the meristem,infection,and nitrogen-fixing regions of the mature nodule.Chemically synthesized MtRGF6p promoted primary root growth in M.truncatula but sup-pressed the growth of L.japonicus primary roots.The peptide negatively affected the initiation of nodule primor-dia,the formation of infection threads,and nodulation in both legumes,with a low dosage showing effects on L.japonicus compared to M.truncatula.These results suggest that the MtRGF6 peptide from M.truncatula may serve as an inter-species signal affecting the root organ development of L.japonicus.