Evidence for thermosensitivity of the cotton (Gossypium hirsutum L.) immature fiber (im) mutant via hypersensitive stomatal activity

Abstract

Thickness of cotton fiber, referred to as fiber maturity, is a key determinant of fiber quality, lint yield, and textile performance. The cotton immature fiber (im) mutant has been used to study fiber maturity since its fiber is thinner than the wild type near isogeneic line (NIL), Texas Marker-1 (TM-1). The im phenotype is caused by a single recessive mutation of a pentatricopeptide repeat (PPR) gene that reduces the activity of mitochondrial complex I and up-regulates stress responsive genes. However, the mechanisms altering the stress responses in im mutant are not well understood. Thus, we characterized growth and gas exchange in im and TM-1 under no stress and also investigated their stress responses by comparing gas exchange and transcriptomic profiles under high temperature. Phenotypic differences were detected between the NILs in non-fiber tissues although less pronounced than the variation in fibers. At near optimum temperature (28±3°C), im maintained the same photosynthetic performance as TM-1 by means of greater stomatal conductance. In contrast, under high temperature stress (>34°C), im leaves reduced photosynthesis by decreasing the stomatal conductance disproportionately more than TM-1. Transcriptomic analyses showed that the genes involved in heat stress responses were differentially expressed between the NIL leaves. These results indicate that the im mutant previously reported to have low activity of mitochondrial complex I displays increased thermosensitivity by impacting stomatal conductance. They also support a notion that mitochondrial complex I activity is required for maintenance of optimal photosynthetic performance and acclimation of plants to high temperature stress. These findings may be useful in the future efforts to understand how physiological mechanisms play a role in determining cotton fiber maturity and may influence stress responses in other crops.

Using landscape genomics to assess local adaptation and genomic vulnerability of a perennial herb Tetrastigma hemsleyanum (Vitaceae) in subtropical China

“…We also identified one candidate SNP linked to a pentatricopeptide repeat ( PPR ) gene. In cotton, a single recessive mutation of a PPR gene reduces the heat accumulation ( Kim et al, 2021 ). In this study, the SNP annotated to the PPR gene showed the highest magnitude of partial allelic turnover in response to GDD (0.88) and served as top-ranked SNPs for growing degree days (9) ( Table 3 ; Supplementary Figure S12 ), suggesting that this PPR gene is among good candidates for further functional studies.…”

Bridging molecular genetics and genomics for cotton fiber quality improvement

“…Error bars are SE. Source : The image was modified from the published reports (Kim, Kato, et al., 2021; Kim, Tang, et al., 2013; Zhang, Chen, et al., 2021).…”

“…Error bars are SE. Source: The image was modified from the published reports (Kim, Kato, et al, 2021;Kim, Tang, et al, 2013;. commercial value of cotton fiber, it is not entirely suitable to examine the biological phenotypes of cotton fibers.…”

“…Recent functional analysis verified that PPR protein (also named GhImA) is responsible for the splicing a mitochondrial mRNA encoding NADH dehydrogenase subunit 7 ( nad7 ) of the mitochondrial complex I, and the level of functional PPR protein is reduced in the im mutant (Figure 5a) (Zhang, Chen, et al., 2021). In addition, phenotypic differences were also detected between the NILs in non‐fiber tissues, although less pronounced than the variation in fiber quality attributes (Kim, Kato, et al., 2021). The high temperature stress reduced photosynthesis more severely in the im leaf by decreasing the stomatal conductance compared with TM‐1 leaf (Figure 5b).…”

Attenuated Total Reflection Fourier Transform Infrared Spectroscopy with Soft Independent Modeling of Class Analogy–Principal Component Analysis for Classifying Cotton Fiber Maturity Phenotypes of Cotton Population Composed of Various Genotypes

“…41 Functional PPR protein is involved in mitochondrial cellular respiration in developing fibers 42 and photosynthetic performance in cotton leaves. 43 The im phenotype was caused by a loss of PPR function in a dosage-dependent manner. 37 Therefore, we suspect that the phenotypic difference between WT-hetero and WT-homo may have resulted from various levels of functional PPR protein.…”