Abstract
Young cotyledons of cotton seedlings are most susceptible to chilling stress. To gain insight into the potential mechanism of cold tolerance of young cotton cotyledons, we conducted physiological and comparative transcriptome analysis of two varieties with contrasting phenotypes. The evaluation of chilling injury of young cotyledons among 74 cotton varieties revealed that H559 was the most tolerant and YM21 was the most sensitive. The physiological analysis found that the ROS scavenging ability was lower, and cell membrane damage was more severe in the cotyledons of YM21 than that of H559 under chilling stress. RNA-seq analysis identified a total of 44,998 expressed genes and 19,982 differentially expressed genes (DEGs) in young cotyledons of the two varieties under chilling stress. Weighted gene coexpression network analysis (WGCNA) of all DEGs revealed four significant modules with close correlation with specific samples. The GO-term enrichment analysis found that lots of genes in H559-specific modules were involved in plant resistance to abiotic stress. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that pathways such as plant hormone signal transduction, MAPK signaling, and plant–pathogen interaction were related to chilling stress response. A total of 574 transcription factors and 936 hub genes in these modules were identified. Twenty hub genes were selected for qRT-PCR verification, revealing the reliability and accuracy of transcriptome data. These findings will lay a foundation for future research on the molecular mechanism of cold tolerance in cotyledons of cotton.
Highlights
Temperature is an essential environmental factor limiting the geographical distribution and growing season of plants [1]
These results suggest that the cold tolerance mechanism of young cotton cotyledon can be complicated, and changes of many physiological parameters in H559 are superior to YM21 in response to chilling stress
We found that some genes related to JA biosynthesis, including LOXs, AOS, and AOC, and genes associated with JA signal transduction including JAR1, JAZ, and MYC2 were predominantly expressed in T24
Summary
Temperature is an essential environmental factor limiting the geographical distribution and growing season of plants [1]. Antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) help eliminate ROS accumulated excessively under abiotic stress to prevent plants from oxidative damage [8] Activities of these antioxidant enzymes are often used as physiological indices for cold tolerance [9]. Scientists have studied the cold response mechanisms of true cotton leaves at the seedling stage and seed embryos at the germination stage by using RNA-seq technology [3,33]. As the first two opposite leaves, are an indispensable part of early cotton seedlings They are the essential autotrophic organs before the first true leaf appeared and the most vulnerable parts to cold stress. Ocfo7ld utpollaenradnccoettoinn veaarrileytiesseaenddlinseglse,ctwede twpeorvfoarmieteides (pHh5y5s9ioalongdicYaMl 2e1x)pweritihmceonntstraasntidngcpohmepnoartyaptievse ftorransuscbrsiepqtuomenet sstueqduieesn. cTiongcomonprethensyiovuelnyguncdoteyrsletadnodnstheofmobloetchulavramrieetcihesa.niTsmhrofucgohldctoomlerpaanrcaetiivne etararlnyscseriepdtloinmges,awnealpyesirsf,orimpedorptahnytsieoxlopgreicsaslioenxppeartimterennst,s saingdnicfoicmanptarpaattivhewtaryasn,scarnipdtohmube sgeeqnueesnwcienrge oidnetnhteifyieodu,nwghciocthylwedoounlds opfrboovtihdevahreielptiefso.rTfhurtouureghrecsoemarpcahraotnivtehteramnsoclericputloamr emaencahlaynsiissm, imopf ocrottatnont ecxoptyrelesdsioon cpoaltdtetronlse,rasingcneifiancadnbt rpeaetdhiwnga.ys, and hub genes were identified, which would provide help for future research on the molecular mechanism of cotton cotyledon cold tolerance and breeding
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