Alpha-amylase (AMY) plays a significant role in regulating the growth, development, and postharvest quality formation in plants. Nevertheless, little is known about the genome-wide features, ...expression patterns, subcellular localization, and functional regulation of AMY genes (MaAMYs) in the common starchy banana (Musa acuminata). Twelve MaAMY proteins from the banana genome database were clustered into two groups and contained a conserved catalytic domain. These MaAMYs formed collinear pairs with the AMYs of maize and rice. Three tandem gene pairs were found within the MaAMYs and are indicative of putative gene duplication events. Cis-acting elements of the MaAMY promoters were found to be involved in phytohormone, development, and stress responses. Furthermore, MaAMY02, 08, 09, and 11 were actively expressed during fruit development and ripening. Specifically, MaAMY11 showed the highest expression level at the middle and later stages of banana ripening. Subcellular localization showed that MaAMY02 and 11 were predominately found in the chloroplast, whereas MaAMY08 and 09 were primarily localized in the cytoplasm. Notably, transient attenuation of MaAMY11 expression resulted in an obvious increase in the starch content of banana fruit, while a significant decrease in starch content was confirmed through the transient overexpression of MaAMY11. Together, these results reveal new insights into the structure, evolution, and expression patterns of the MaAMY family, affirming the functional role of MaAMY11 in the starch degradation of banana fruit.
Sugars Will Eventually be Exported Transporters (SWEET) are a novel type of sugar transporter that plays crucial roles in multiple biological processes. From banana, for the first time, 25 SWEET ...genes which could be classified into four subfamilies were identified. Majority of MaSWEETs in each subfamily shared similar gene structures and conserved motifs. Comprehensive transcriptomic analysis of two banana genotypes revealed differential expression patterns of MaSWEETs in different tissues, at various stages of fruit development and ripening, and in response to abiotic and biotic stresses. More than 80% MaSWEETs were highly expressed in BaXi Jiao (BX, Musa acuminata AAA group, cv. Cavendish), in sharp contrast to Fen Jiao (FJ, M. acuminata AAB group) when pseudostem was first emerged. However, MaSWEETs in FJ showed elevated expression under cold, drought, salt, and fungal disease stresses, but not in BX. Interaction networks and co-expression assays further revealed that MaSWEET-mediated networks participate in fruit development signaling and abiotic/biotic stresses, which was strongly activated during early stage of fruit development in BX. This study provides new insights into the complex transcriptional regulation of SWEETs, as well as numerous candidate genes that promote early sugar transport to improve fruit quality and enhance stress resistance in banana.
ADP-glucose pyrophosphorylase (AGPase) is the first rate-limiting enzyme in starch biosynthesis and plays crucial roles in multiple biological processes. Despite its importance, AGPase is poorly ...studied in starchy fruit crop banana (
L.). In this study, eight
genes have been identified genome-wide in
, which could be clustered into the large (APL) and small (APS) subunits. Comprehensive transcriptomic analysis revealed temporal and spatial expression variations of
and
and their differential responses to abiotic/biotic stresses in two banana genotypes, Fen Jiao (FJ) and BaXi Jiao (BX).
showed generally high expression at various developmental and ripening stages and in response to abiotic/biotic stresses in both genotypes.
and
were specifically induced by abiotic stresses including cold, salt, and drought, as well as by fungal infection in FJ, but not in BX. The presence of hormone-related and stress-relevant
-acting elements in the promoters of
genes suggests that
may play an important role in multiple biological processes. Taken together, this study provides new insights into the complex transcriptional regulation of
, underlying their key roles in promoting starch biosynthesis and enhancing stress tolerance in banana.
Rho-like GTPases from plants (ROPs) are plant-specific molecular switches that are crucial for plant survival when subjected to abiotic stress. We identified and characterized 17 novel ROP proteins ...from
(MaROPs) using genomic techniques. The identified MaROPs fell into three of the four previously described ROP groups (Groups II⁻IV), with MaROPs in each group having similar genetic structures and conserved motifs. Our transcriptomic analysis showed that the two banana genotypes tested, Fen Jiao and BaXi Jiao, had similar responses to abiotic stress: Six genes (
,
,
,
,
, and
) were highly expressed in response to cold, salt, and drought stress conditions in both genotypes. Of these,
was most highly expressed in response to salt stress. Co-localization experiments showed that the MaROP5g protein was localized at the plasma membrane. When subjected to salt stress, transgenic
overexpressing
had longer primary roots and increased survival rates compared to wild-type
. The increased salt tolerance conferred by
might be related to reduced membrane injury and the increased cytosolic K⁺/Na⁺ ratio and Ca
concentration in the transgenic plants as compared to wild-type. The increased expression of salt overly sensitive (SOS)-pathway genes and calcium-signaling pathway genes in
-overexpressing
reflected the enhanced tolerance to salt stress by the transgenic lines in comparison to wild-type. Collectively, our results suggested that abiotic stress tolerance in banana plants might be regulated by multiple
, and that
might enhance salt tolerance by increasing root length, improving membrane injury and ion distribution.
Granule-bound starch synthase (GBSS) is responsible for amylose synthesis, but the role of GBSS genes and their encoded proteins remains poorly understood in banana. In this study, amylose content ...and GBSS activity gradually increased during development of the banana fruit, and decreased during storage of the mature fruit. GBSS protein in banana starch granules was approximately 55.0 kDa. The protein was up-regulated expression during development while it was down-regulated expression during storage. Six genes, designated as MaGBSSI-1, MaGBSSI-2, MaGBSSI-3, MaGBSSI-4, MaGBSSII-1, and MaGBSSII-2, were cloned and characterized from banana fruit. Among the six genes, the expression pattern of MaGBSSI-3 was the most consistent with the changes in amylose content, GBSS enzyme activity, GBSS protein levels, and the quantity or size of starch granules in banana fruit. These results suggest that MaGBSSI-3 might regulate amylose metabolism by affecting the variation of GBSS levels and the quantity or size of starch granules in banana fruit during development or storage.
Abstract
Starch branching enzyme (SBE) has rarely been studied in common starchy banana fruits. For the first time, we report here the molecular characterization of seven
SBE
(
MaSBE
) and six
SBE
(
...MbSBE
) genes in the banana A- and B-genomes, respectively, which could be classified into three distinct subfamilies according to genome-wide identification. Systematic transcriptomic analysis revealed that six
MaSBE
s and six
MbSBE
s were expressed in the developing banana fruits of two different genotypes, BaXi Jiao (BX, AAA) and Fen Jiao (FJ, AAB), among which
MaSBE2.3
and
MbSBE2.3
were highly expressed. Transient silencing of
MaSBE2.3
expression in banana fruit discs led to a significant decrease in its transcription, which coincides with significant reductions in total starch and amylopectin contents compared to those of empty vector controls. The suggested functional role of
MaSBE2.3
in banana fruit development was corroborated by its transient overexpression in banana fruit discs, which led to significant enhancements in total starch and amylopectin contents. A number of transcription factors, including three auxin response factors (ARF2/12/24) and two MYBs (MYB3/308), that interact with the
MaSBE2.3
promoter were identified by yeast one-hybrid library assays. Among these ARFs and MYBs, MaARF2/MaMYB308 and MaARF12/MaARF24/MaMYB3 were demonstrated via a luciferase reporter system to upregulate and downregulate the expression of
MaSBE2.3
, respectively.
Abiotic stress is the focus of research on passion fruit characters because of its damage to the industry. Basic helix-loop-helix (bHLH) is one of the Transcription factors (TFs) which can act in an ...anti-abiotic stress role through diverse biological processes. However, no systemic analysis of the passion fruit bHLH (PebHLH) family was reported. In this study, 117 PebHLH members were identified from the genome of passion fruit, related to plant stress resistance and development by prediction of protein interaction. Furthermore, the transcriptome sequencing results showed that the PebHLHs responded to different abiotic stresses. At different ripening stages of passion fruit, the expression level of most PebHLHs in the immature stage (T1) was higher than that in the mature stage (T2 and T3). Eight PebHLHs with differentially expressed under different stress treatments and different ripening stages were selected and verified by qRT-PCR. In this research, the expression of one member, PebHLH56, was induced under cold stress. Further, the promoter of PebHLH56 was fused to β-Galactosidase (GUS) to generate the expression vector that was transformed into Arabidopsis. It showed that PebHLH56 could significantly respond to cold stress. This study provided new insights into the regulatory functions of PebHLH genes during fruit maturity stages and abiotic stress, thereby improving the understanding of the characteristics and evolution of the PebHLH gene family.
The NAC (NAM, ATAF and CUC) gene family plays an important role in plant development and abiotic stress response. However, up to now, the identification and research of the NAC (
) family members of ...passion fruit are still lacking. In this study, 25
were identified from the passion fruit genome, and their functions under abiotic stress and at different fruit-ripening stages were analyzed. Furthermore, we analyzed the transcriptome sequencing results of
under four various abiotic stresses (drought, salt, cold and high temperature) and three different fruit-ripening stages, and verified the expression results of some genes by qRT-PCR. Additionally, tissue-specific analysis showed that most
were mainly expressed in flowers. In particular,
was induced by four various abiotic stresses. At present, low temperatures have seriously endangered the development of passion fruit cultivation. Therefore,
was transformed into tobacco, yeast and Arabidopsis to study their function of resisting low temperature. The results show that
responded to cold stress significantly in tobacco and Arabidopsis, and could improve the low temperature tolerance of yeast. This study not only improved the understanding of the
gene family characteristics and evolution, but also provided new insights into the regulation of the
gene at different stages of fruit maturation and abiotic stresses.
The abscisic acid (ABA)-, stress-, and ripening-induced (ASR) protein is a plant-specific hydrophilic transcriptional factor involved in fruit ripening and the abiotic stress response. To date, there ...have been no studies on the role of ASR genes in delayed flowering time. Here, we found that the ASR from banana, designated as MaASR, was preferentially expressed in the banana female flowers from the eighth, fourth, and first cluster of the inflorescence. MaASR transgenic lines (L14 and L38) had a clear delayed-flowering phenotype. The number of rosette leaves, sepals, and pedicel trichomes in L14 and L38 was greater than in the wild type (WT) under long day (LD) conditions. The period of buds, mid-flowers, and full bloom of L14 and L38 appeared later than the WT. cDNA microarray and quantitative real-time PCR (qRT-PCR) analyses revealed that overexpression of MaASR delays flowering through reduced expression of several genes, including photoperiod pathway genes, vernalization pathway genes, gibberellic acid pathway genes, and floral integrator genes, under short days (SD) for 28 d (from vegetative to reproductive transition stage); however, the expression of the autonomous pathway genes was not affected. This study provides the first evidence of a role for ASR genes in delayed flowering time in plants.
β-amylase (BAM) is an important enzyme involved in conversion of starch to maltose in multiple biological processes in plants. However, there is currently insufficient information on the BAM gene ...family in the important fruit crop banana. This study identified 16 BAM genes in the banana genome. Phylogenetic analysis showed that MaBAMs were classified into four subfamilies. Most MaBAMs in each subfamily shared similar gene structures. Conserved motif analysis showed that all identified MaBAM proteins had the typical glyco hydro 14 domains. Comprehensive transcriptomic analysis of two banana genotypes revealed the expression patterns of MaBAMs in different tissues, at various stages of fruit development and ripening, and in responses to abiotic stresses. Most MaBAMs showed strong transcript accumulation changes during fruit development and late-stage ripening. Some MaBAMs showed significant changes under cold, salt, and osmotic stresses. This finding indicated that MaBAMs might be involved in regulating fruit development, ripening, and responses to abiotic stress. Analysis of five hormone-related and seven stress-relevant elements in the promoters of MaBAMs further revealed that BAMs participated in various biological processes. This systemic analysis provides new insights into the transcriptional characteristics of the BAM genes in banana and may serve as a basis for further functional studies of such genes.
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