Low temperature (LT) in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.  Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting.  These included morphological observation, measurements of starch synthase activity, and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting.  Additionally, proteomic analysis was performed using tandem mass tags (TMT).  Results showed that the plumpness of wheat grains decreased after LT stress.  Moreover, the activities of sucrose synthase (SuS, EC 2.4.1.13) and ADP-glucose pyrophosphorylase (AGPase, EC 2.7.7.27) exhibited a significant reduction, leading to a significant reduction in the contents of amylose and amylopectin.  A total of 509 differentially expressed proteins (DEPs) were identified by proteomics analysis.  The Gene Ontology (GO) enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions, and the up-regulated seed storage protein (SSP) played an active role in the response of grains to LT stress and subsequent damage.  The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase (SPS), glucose-1-phosphate adenylyltransferase (glgC), and β-fructofuranosidase (FFase) in sucrose and starch metabolic pathways, thus affecting the synthesis of grain starch.  In addition, many heat shock proteins (HSPs) were found in the protein processing in endoplasmic reticulum pathways, which can resist some damage caused by LT stress.  These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield development after exposure to LT stress in spring.

Pectin is a major constituent of the plant cell wall.  Pectate lyase (PEL, EC 4.2.2.2) uses anti-β-elimination chemistry to cleave the α-1,4 glycosidic linkage in the homogalacturonan region of pectin.  However, limited information is available on the comprehensive and evolutionary analysis of PELs in the Malvaceae.  In this study, we identified 597 PEL genes from 10 Malvaceae species.  Phylogenetic and motif analyses revealed that these PELs are classified into six subfamilies: Clades I, II, III, IV, Va, and Vb.  The two largest subfamilies, Clades I and II, contained 237 and 222 PEL members, respectively.  The members of Clades Va and Vb only contained four or five motifs, far fewer than the other subfamilies.  Gene duplication analysis showed that segmental duplication played a crucial role in the expansion of the PEL gene family in Gossypium species.  The PELs from Clades I, IV, Va, and Vb were expressed during the fiber elongation stage, but nearly all PEL genes from Clades II and III showed no expression in any of the investigated fiber developmental stages.  We further performed single-gene haplotype association analysis in 2,001 G. hirsutum accessions and 229 G. barbadense accessions.  Interestingly, 14 PELs were significantly associated with fiber length and strength traits in G. barbadense with superior fiber quality, while only eight GhPEL genes were found to be significantly associated with fiber quality traits in G. hirsutum.  Our findings provide important information for further evolutionary and functional research on the PEL gene family members and their potential use for fiber quality improvement in cotton.