Two Paralogous Genes Encoding Auxin Efflux Carrier Differentially Expressed in Bitter Gourd (Momordica charantia)

Yi-Li Li,Pung-Ling Huang,Yun-Shan Lin,Yi-Yin Do

doi:10.3390/ijms18112343

Yi-Li Li, Pung-Ling Huang + Show 2 more

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https://doi.org/10.3390/ijms18112343

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Abstract

The phytohormone auxin regulates various developmental programs in plants, including cell growth, cell division and cell differentiation. The auxin efflux carriers are essential for the auxin transport. To show an involvement of auxin transporters in the coordination of fruit development in bitter gourd, a juicy fruit, we isolated novel cDNAs (referred as McPIN) encoding putative auxin efflux carriers, including McPIN1, McPIN2 (allele of McPIN1) and McPIN3, from developing fruits of bitter gourd. Both McPIN1 and McPIN3 genes possess six exons and five introns. Hydropathy analysis revealed that both polypeptides have two hydrophobic regions with five transmembrane segments and a predominantly hydrophilic core. Phylogenetic analyses revealed that McPIN1 shared the highest homology to the group of Arabidopsis, cucumber and tomato PIN1, while McPIN3 belonged to another group, including Arabidopsis and tomato PIN3 as well as PIN4. This suggests different roles for McPIN1 and McPIN3 in auxin transport involved in the fruit development of bitter gourd. Maximum mRNA levels for both genes were detected in staminate and pistillate flowers. McPIN1 is expressed in a particular period of early fruit development but McPIN3 continues to be expressed until the last stage of fruit ripening. Moreover, these two genes are auxin-inducible and qualified as early auxin-response genes. Their expression patterns suggest that these two auxin transporter genes play a pivotal role in fruit setting and development.

Highlights

Auxins are plant hormones that mediate many aspects of plant growth and development
To isolate the fruit-related auxin efflux carrier genes, the cDNA library constructed by poly(A)+ RNA extracted from fruit of bitter gourd was screened using Arabidopsis AtPIN1 and AtPIN2 fragments as probes
Among the cDNA clones obtained, pMAEC28, pMAEC43 and pMAEC93 were selected for complete nucleotide sequence analysis

Summary

Introduction

Auxins are plant hormones that mediate many aspects of plant growth and development. Stem growth, cell division in the cambium, differentiation of phloem and xylem, root initiation and growth of flower parts. These hormones delay leaf senescence and are involved in apical dominance and leaf abscission. As early as 1926, Cholodny and Went proposed that the gravitropic curvature of plant organs was dependent upon lateral transport of the plant hormone indole-3-acetic acid (IAA)—auxin—from the upper to the lower side of a responding organ, resulting in different auxin concentration on the two sides of the organ. Different auxin levels result in different elongation rates and, change the growth curvature [2]

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