No abstract

Naturally colored cotton (Gossypium hirsutum L.) fibers (CCFs) are of interest in the textile industry because they require little dyeing and result in less environmental pollution. Pigmentation is one of the most important factors that differentiate CCFs from white cotton fiber (WCF) during fiber maturation. Many factors are involved in pigmentation, some of which we compared between CCFs and WCF with isogenetic backgrounds. These included the type of pigment, the activity of phenylalanine ammonia lyase (PAL), the concentration of total carbohydrates, and the type of soluble saccharide. We aimed to determine the causes of different fiber colors and found that flavonoids were the dominant type of pigment in the CCFs. At maturity (50 d post anthesis [DPA]), the WCF had only about 1/3 the amount of flavonoids as the brown cotton fiber (BCF) and 1/10 that of the green cotton fiber (GCF). During the course of fiber maturation (in particular, the stage before 8 DPA), CCFs had much higher PAL activity than the WCF. Of the fibers, the GCF had the highest concentration of carbohydrates over the course of maturation. However, higher concentrations of total carbohydrates did not always lead to higher concentrations of cellulose. This was very likely due to the synthesis of flavonoids and their derivatives consuming a large amount of carbohydrates that otherwise might be used for the synthesis of cellulose.

HighlightGhNAP could regulate leaf senescence via the ABA-mediated pathways and is related to the yield and quality of cotton.

NAC (NAM, ATAF1, 2 and CUC2) family is a plant-specific transcription factor and it controls various plant developmental processes. In the current study, 124 NAC members were identified in Zea mays and were phylogenetically clustered into 13 distinct subfamilies. The whole genome duplication (WGD), especially an additional WGD event, may lead to expanding ZmNAC members. Different subfamily has different expansion rate, and NAC subfamily preference was found during the expansion in maize. Moreover, the duplication events might occur after the divergence of the lineages of Z. mays and S. italica, and segmental duplication seemed to be the dominant pattern for the gene duplication in maize. Furthermore, the expansion of ZmNAC members may be also related to gain and loss of introns. Besides, the restriction of functional divergence was discovered after most of the gene duplication events. These results could provide novel insights into molecular evolution and expansion analysis of NAC family in maize, and advance the NAC researches in other plants, especially polyploid plants.

Plant non-specific lipid transfer proteins (nsLTPs) are involved in many biological processes. In this study, 51, 47 and 91 nsLTPs were identified in Gossypium arboreum, G. raimondii and their descendant allotetraploid G. hirsutum, respectively. All the nsLTPs were phylogenetically divided into 8 distinct subfamilies. Besides, the recent duplication, which is considered cotton-specific whole genome duplication, may have led to nsLTP expansion in Gossypium. Both tandem and segmental duplication contributed to nsLTP expansion in G. arboreum and G. hirsutum, while tandem duplication was the dominant pattern in G. raimondii. Additionally, the interspecific orthologous gene pairs in Gossypium were identified. Some GaLTPs and GrLTPs lost their orthologs in the At and Dt subgenomes, respectively, of G. hirsutum. The distribution of these GrLTPs and GaLTPs within each subfamily was complementary, suggesting that the loss and retention of nsLTPs in G. hirsutum might not be random. Moreover, the nsLTPs in the At and Dt subgenomes might have evolved symmetrically. Furthermore, both intraspecific and interspecific orthologous genes showed considerable expression variation, suggesting that their functions were strongly differentiated. Our results lay an important foundation for expansion and evolutionary analysis of the nsLTP family in Gossypium, and advance nsLTP studies in other plants, especially polyploid plants.